gpu: implement automatic mipmaps for images

All GPU APIs except OpenGL ES 2 can generate mipmaps for textures.
This trades 33% more GPU memory use for improved rendering quality
and speed for downscaled images.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/gpu.go

@@ -436,7 +436,7 @@ func (r *renderer) texHandle(cache *resourceCache, data imageOpData) driver.Text
 	if tex.tex != nil {
 		return tex.tex
 	}
-	handle, err := r.ctx.NewTexture(driver.TextureFormatSRGBA, data.src.Bounds().Dx(), data.src.Bounds().Dy(), driver.FilterLinear, driver.FilterLinear, driver.BufferBindingTexture)
+	handle, err := r.ctx.NewTexture(driver.TextureFormatSRGBA, data.src.Bounds().Dx(), data.src.Bounds().Dy(), driver.FilterLinearMipmapLinear, driver.FilterLinear, driver.BufferBindingTexture)
 	if err != nil {
 		panic(err)
 	}

gpu/internal/d3d11/d3d11_windows.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"image"
 	"math"
+	"math/bits"
 	"unsafe"
 
 	"golang.org/x/sys/windows"
@@ -58,6 +59,7 @@ type Texture struct {
 
 	width   int
 	height  int
+	mipmap  bool
 	foreign bool
 }
 
@@ -219,17 +221,33 @@ func (b *Backend) NewTexture(format driver.TextureFormat, width, height int, min
 	default:
 		return nil, fmt.Errorf("unsupported texture format %d", format)
 	}
+	bindFlags := convBufferBinding(bindings)
+	miscFlags := uint32(0)
+	mipmap := minFilter == driver.FilterLinearMipmapLinear
+	nmipmaps := 1
+	if mipmap {
+		// Flags required by ID3D11DeviceContext::GenerateMips.
+		bindFlags |= d3d11.BIND_SHADER_RESOURCE | d3d11.BIND_RENDER_TARGET
+		miscFlags |= d3d11.RESOURCE_MISC_GENERATE_MIPS
+		dim := width
+		if height > dim {
+			dim = height
+		}
+		log2 := 32 - bits.LeadingZeros32(uint32(dim)) - 1
+		nmipmaps = log2 + 1
+	}
 	tex, err := b.dev.CreateTexture2D(&d3d11.TEXTURE2D_DESC{
 		Width:     uint32(width),
 		Height:    uint32(height),
-		MipLevels: 1,
+		MipLevels: uint32(nmipmaps),
 		ArraySize: 1,
 		Format:    d3dfmt,
 		SampleDesc: d3d11.DXGI_SAMPLE_DESC{
 			Count:   1,
 			Quality: 0,
 		},
-		BindFlags: convBufferBinding(bindings),
+		BindFlags: bindFlags,
+		MiscFlags: miscFlags,
 	})
 	if err != nil {
 		return nil, err
@@ -247,6 +265,8 @@ func (b *Backend) NewTexture(format driver.TextureFormat, width, height int, min
 			filter = d3d11.FILTER_MIN_MAG_MIP_POINT
 		case minFilter == driver.FilterLinear && magFilter == driver.FilterLinear:
 			filter = d3d11.FILTER_MIN_MAG_LINEAR_MIP_POINT
+		case minFilter == driver.FilterLinearMipmapLinear && magFilter == driver.FilterLinear:
+			filter = d3d11.FILTER_MIN_MAG_MIP_LINEAR
 		default:
 			d3d11.IUnknownRelease(unsafe.Pointer(tex), tex.Vtbl.Release)
 			return nil, fmt.Errorf("unsupported texture filter combination %d, %d", minFilter, magFilter)
@@ -325,7 +345,7 @@ func (b *Backend) NewTexture(format driver.TextureFormat, width, height int, min
 			return nil, err
 		}
 	}
-	return &Texture{backend: b, format: d3dfmt, tex: tex, sampler: sampler, resView: resView, uaView: uaView, renderTarget: fbo, bindings: bindings, width: width, height: height}, nil
+	return &Texture{backend: b, format: d3dfmt, tex: tex, sampler: sampler, resView: resView, uaView: uaView, renderTarget: fbo, bindings: bindings, width: width, height: height, mipmap: mipmap}, nil
 }
 
 func (b *Backend) newInputLayout(vertexShader shader.Sources, layout []driver.InputDesc) (*d3d11.InputLayout, error) {
@@ -609,6 +629,9 @@ func (t *Texture) Upload(offset, size image.Point, pixels []byte, stride int) {
 	}
 	res := (*d3d11.Resource)(unsafe.Pointer(t.tex))
 	t.backend.ctx.UpdateSubresource(res, dst, uint32(stride), uint32(len(pixels)), pixels)
+	if t.mipmap {
+		t.backend.ctx.GenerateMips(t.resView)
+	}
 }
 
 func (t *Texture) Release() {

gpu/internal/driver/driver.go

@@ -166,6 +166,7 @@ const (
 const (
 	FilterNearest TextureFilter = iota
 	FilterLinear
+	FilterLinearMipmapLinear
 )
 
 const (

gpu/internal/metal/metal_darwin.go

@@ -239,6 +239,14 @@ static void blitEncCopyBufferToTexture(CFTypeRef blitEncRef, CFTypeRef bufRef, C
 	}
 }
 
+static void blitEncGenerateMipmapsForTexture(CFTypeRef blitEncRef, CFTypeRef texRef) {
+	@autoreleasepool {
+		id<MTLBlitCommandEncoder> enc = (__bridge id<MTLBlitCommandEncoder>)blitEncRef;
+		id<MTLTexture> tex = (__bridge id<MTLTexture>)texRef;
+		[enc generateMipmapsForTexture: tex];
+	}
+}
+
 static void blitEncCopyTextureToBuffer(CFTypeRef blitEncRef, CFTypeRef texRef, CFTypeRef bufRef, NSUInteger offset, NSUInteger stride, NSUInteger length, MTLSize dims, MTLOrigin orig) {
 	@autoreleasepool {
 		id<MTLBlitCommandEncoder> enc = (__bridge id<MTLBlitCommandEncoder>)blitEncRef;
@@ -269,25 +277,26 @@ static void blitEncCopyBufferToBuffer(CFTypeRef blitEncRef, CFTypeRef srcRef, CF
 	}
 }
 
-static CFTypeRef newTexture(CFTypeRef devRef, NSUInteger width, NSUInteger height, MTLPixelFormat format, MTLTextureUsage usage) {
+static CFTypeRef newTexture(CFTypeRef devRef, NSUInteger width, NSUInteger height, MTLPixelFormat format, MTLTextureUsage usage, int mipmapped) {
 	@autoreleasepool {
 		id<MTLDevice> dev = (__bridge id<MTLDevice>)devRef;
 		MTLTextureDescriptor *mtlDesc = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat: format
 																						   width: width
 																						  height: height
-																				   	   mipmapped: NO];
+																				   	   mipmapped: mipmapped ? YES : NO];
 		mtlDesc.usage = usage;
 		mtlDesc.storageMode =  MTLStorageModePrivate;
 		return CFBridgingRetain([dev newTextureWithDescriptor:mtlDesc]);
 	}
 }
 
-static CFTypeRef newSampler(CFTypeRef devRef, MTLSamplerMinMagFilter minFilter, MTLSamplerMinMagFilter magFilter) {
+static CFTypeRef newSampler(CFTypeRef devRef, MTLSamplerMinMagFilter minFilter, MTLSamplerMinMagFilter magFilter, MTLSamplerMipFilter mipFilter) {
 	@autoreleasepool {
 		id<MTLDevice> dev = (__bridge id<MTLDevice>)devRef;
 		MTLSamplerDescriptor *desc = [MTLSamplerDescriptor new];
 		desc.minFilter = minFilter;
 		desc.magFilter = magFilter;
+		desc.mipFilter = mipFilter;
 		return CFBridgingRetain([dev newSamplerStateWithDescriptor:desc]);
 	}
 }
@@ -405,6 +414,7 @@ type Texture struct {
 	sampler C.CFTypeRef
 	width   int
 	height  int
+	mipmap  bool
 	foreign bool
 }
 
@@ -581,26 +591,33 @@ func (b *Backend) NewTexture(format driver.TextureFormat, width, height int, min
 	if bindings&driver.BufferBindingShaderStorageWrite != 0 {
 		usage |= C.MTLTextureUsageShaderWrite
 	}
-	tex := C.newTexture(b.dev, C.NSUInteger(width), C.NSUInteger(height), mformat, usage)
+	min, mip := samplerFilterFor(minFilter)
+	max, _ := samplerFilterFor(magFilter)
+	mipmap := mip != C.MTLSamplerMipFilterNotMipmapped
+	mipmapped := C.int(0)
+	if mipmap {
+		mipmapped = 1
+	}
+	tex := C.newTexture(b.dev, C.NSUInteger(width), C.NSUInteger(height), mformat, usage, mipmapped)
 	if tex == 0 {
 		return nil, errors.New("metal: [MTLDevice newTextureWithDescriptor:] failed")
 	}
-	min := samplerFilterFor(minFilter)
+	s := C.newSampler(b.dev, min, max, mip)
-	max := samplerFilterFor(magFilter)
-	s := C.newSampler(b.dev, min, max)
 	if s == 0 {
 		C.CFRelease(tex)
 		return nil, errors.New("metal: [MTLDevice newSamplerStateWithDescriptor:] failed")
 	}
-	return &Texture{backend: b, texture: tex, sampler: s, width: width, height: height}, nil
+	return &Texture{backend: b, texture: tex, sampler: s, width: width, height: height, mipmap: mipmap}, nil
 }
 
-func samplerFilterFor(f driver.TextureFilter) C.MTLSamplerMinMagFilter {
+func samplerFilterFor(f driver.TextureFilter) (C.MTLSamplerMinMagFilter, C.MTLSamplerMipFilter) {
 	switch f {
 	case driver.FilterNearest:
-		return C.MTLSamplerMinMagFilterNearest
+		return C.MTLSamplerMinMagFilterNearest, C.MTLSamplerMipFilterNotMipmapped
 	case driver.FilterLinear:
-		return C.MTLSamplerMinMagFilterLinear
+		return C.MTLSamplerMinMagFilterLinear, C.MTLSamplerMipFilterNotMipmapped
+	case driver.FilterLinearMipmapLinear:
+		return C.MTLSamplerMinMagFilterLinear, C.MTLSamplerMipFilterLinear
 	default:
 		panic("invalid texture filter")
 	}
@@ -900,6 +917,9 @@ func (t *Texture) Upload(offset, size image.Point, pixels []byte, stride int) {
 		depth:  1,
 	}
 	C.blitEncCopyBufferToTexture(enc, buf, t.texture, C.NSUInteger(off), C.NSUInteger(dstStride), C.NSUInteger(len(store)), msize, orig)
+	if t.mipmap {
+		C.blitEncGenerateMipmapsForTexture(enc, t.texture)
+	}
 }
 
 func (t *Texture) Release() {

gpu/internal/opengl/opengl.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"image"
+	"math/bits"
 	"runtime"
 	"strings"
 	"time"
@@ -105,6 +106,7 @@ type texture struct {
 	triple   textureTriple
 	width    int
 	height   int
+	mipmap   bool
 	bindings driver.BufferBinding
 	foreign  bool
 }
@@ -695,13 +697,29 @@ func (b *Backend) NewTexture(format driver.TextureFormat, width, height int, min
 		return nil, errors.New("unsupported texture format")
 	}
 	b.BindTexture(0, tex)
-	b.funcs.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, toTexFilter(magFilter))
+	min, mipmap := toTexFilter(minFilter)
-	b.funcs.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, toTexFilter(minFilter))
+	mag, _ := toTexFilter(magFilter)
+	if b.gles && b.glver[0] < 3 {
+		// OpenGL ES 2 only supports mipmaps for power-of-two textures.
+		mipmap = false
+	}
+	tex.mipmap = mipmap
+	b.funcs.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, mag)
+	b.funcs.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, min)
 	b.funcs.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE)
 	b.funcs.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE)
-	if b.gles && b.glver[0] >= 3 {
+	if mipmap {
+		nmipmaps := 1
+		if mipmap {
+			dim := width
+			if height > dim {
+				dim = height
+			}
+			log2 := 32 - bits.LeadingZeros32(uint32(dim)) - 1
+			nmipmaps = log2 + 1
+		}
 		// Immutable textures are required for BindImageTexture, and can't hurt otherwise.
-		b.funcs.TexStorage2D(gl.TEXTURE_2D, 1, tex.triple.internalFormat, width, height)
+		b.funcs.TexStorage2D(gl.TEXTURE_2D, nmipmaps, tex.triple.internalFormat, width, height)
 	} else {
 		b.funcs.TexImage2D(gl.TEXTURE_2D, 0, tex.triple.internalFormat, width, height, tex.triple.format, tex.triple.typ)
 	}
@@ -1195,12 +1213,14 @@ func (p *pipeline) Release() {
 	*p = pipeline{}
 }
 
-func toTexFilter(f driver.TextureFilter) int {
+func toTexFilter(f driver.TextureFilter) (int, bool) {
 	switch f {
 	case driver.FilterNearest:
-		return gl.NEAREST
+		return gl.NEAREST, false
 	case driver.FilterLinear:
-		return gl.LINEAR
+		return gl.LINEAR, false
+	case driver.FilterLinearMipmapLinear:
+		return gl.LINEAR_MIPMAP_LINEAR, true
 	default:
 		panic("unsupported texture filter")
 	}
@@ -1234,6 +1254,9 @@ func (t *texture) Upload(offset, size image.Point, pixels []byte, stride int) {
 	}
 	t.backend.glstate.pixelStorei(t.backend.funcs, gl.UNPACK_ROW_LENGTH, rowLen)
 	t.backend.funcs.TexSubImage2D(gl.TEXTURE_2D, 0, offset.X, offset.Y, size.X, size.Y, t.triple.format, t.triple.typ, pixels)
+	if t.mipmap {
+		t.backend.funcs.GenerateMipmap(gl.TEXTURE_2D)
+	}
 }
 
 func (t *timer) Begin() {

gpu/internal/vulkan/vulkan.go

@@ -10,6 +10,7 @@ import (
 	"errors"
 	"fmt"
 	"image"
+	"math/bits"
 
 	"gioui.org/gpu/internal/driver"
 	"gioui.org/internal/vk"
@@ -75,6 +76,7 @@ type Texture struct {
 	sampler    vk.Sampler
 	fbo        vk.Framebuffer
 	format     vk.Format
+	mipmaps    int
 	layout     vk.ImageLayout
 	passLayout vk.ImageLayout
 	width      int
@@ -155,7 +157,7 @@ func newVulkanDevice(api driver.Vulkan) (driver.Device, error) {
 	if props&reqs == reqs {
 		b.caps |= driver.FeatureFloatRenderTargets
 	}
-	reqs = vk.FORMAT_FEATURE_COLOR_ATTACHMENT_BLEND_BIT | vk.FORMAT_FEATURE_SAMPLED_IMAGE_BIT
+	reqs = vk.FORMAT_FEATURE_COLOR_ATTACHMENT_BLEND_BIT | vk.FORMAT_FEATURE_SAMPLED_IMAGE_BIT | vk.FORMAT_FEATURE_SAMPLED_IMAGE_FILTER_LINEAR_BIT
 	props = vk.GetPhysicalDeviceFormatProperties(b.physDev, vk.FORMAT_R8G8B8A8_SRGB)
 	if props&reqs == reqs {
 		b.caps |= driver.FeatureSRGB
@@ -292,19 +294,31 @@ func (b *Backend) NewTexture(format driver.TextureFormat, width, height int, min
 		usage |= vk.IMAGE_USAGE_STORAGE_BIT
 	}
 	filterFor := func(f driver.TextureFilter) vk.Filter {
-		switch minFilter {
+		switch f {
-		case driver.FilterLinear:
+		case driver.FilterLinear, driver.FilterLinearMipmapLinear:
 			return vk.FILTER_LINEAR
 		case driver.FilterNearest:
 			return vk.FILTER_NEAREST
 		}
 		panic("unknown filter")
 	}
-	sampler, err := vk.CreateSampler(b.dev, filterFor(minFilter), filterFor(magFilter))
+	mipmapMode := vk.SAMPLER_MIPMAP_MODE_NEAREST
+	mipmap := minFilter == driver.FilterLinearMipmapLinear
+	nmipmaps := 1
+	if mipmap {
+		mipmapMode = vk.SAMPLER_MIPMAP_MODE_LINEAR
+		dim := width
+		if height > dim {
+			dim = height
+		}
+		log2 := 32 - bits.LeadingZeros32(uint32(dim)) - 1
+		nmipmaps = log2 + 1
+	}
+	sampler, err := vk.CreateSampler(b.dev, filterFor(minFilter), filterFor(magFilter), mipmapMode)
 	if err != nil {
 		return nil, mapErr(err)
 	}
-	img, mem, err := vk.CreateImage(b.physDev, b.dev, vkfmt, width, height, usage)
+	img, mem, err := vk.CreateImage(b.physDev, b.dev, vkfmt, width, height, nmipmaps, usage)
 	if err != nil {
 		vk.DestroySampler(b.dev, sampler)
 		return nil, mapErr(err)
@@ -316,7 +330,7 @@ func (b *Backend) NewTexture(format driver.TextureFormat, width, height int, min
 		vk.FreeMemory(b.dev, mem)
 		return nil, mapErr(err)
 	}
-	t := &Texture{backend: b, img: img, mem: mem, view: view, sampler: sampler, layout: vk.IMAGE_LAYOUT_UNDEFINED, passLayout: passLayout, width: width, height: height, format: vkfmt}
+	t := &Texture{backend: b, img: img, mem: mem, view: view, sampler: sampler, layout: vk.IMAGE_LAYOUT_UNDEFINED, passLayout: passLayout, width: width, height: height, format: vkfmt, mipmaps: nmipmaps}
 	if bindings&driver.BufferBindingFramebuffer != 0 {
 		pass, err := vk.CreateRenderPass(b.dev, vkfmt, vk.ATTACHMENT_LOAD_OP_DONT_CARE,
 			vk.IMAGE_LAYOUT_UNDEFINED, vk.IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL, nil)
@@ -646,6 +660,40 @@ func (t *Texture) Upload(offset, size image.Point, pixels []byte, stride int) {
 		vk.ACCESS_TRANSFER_WRITE_BIT,
 	)
 	vk.CmdCopyBufferToImage(cmdBuf, stage.buf, t.img, t.layout, op)
+	// Build mipmaps by repeating linear blits.
+	w, h := t.width, t.height
+	for i := 1; i < t.mipmaps; i++ {
+		nw, nh := w/2, h/2
+		if nh < 1 {
+			nh = 1
+		}
+		if nw < 1 {
+			nw = 1
+		}
+		// Transition previous (source) level.
+		b := vk.BuildImageMemoryBarrier(
+			t.img,
+			vk.ACCESS_TRANSFER_WRITE_BIT, vk.ACCESS_TRANSFER_READ_BIT,
+			vk.IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL, vk.IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL,
+			i-1, 1,
+		)
+		vk.CmdPipelineBarrier(cmdBuf, vk.PIPELINE_STAGE_TRANSFER_BIT, vk.PIPELINE_STAGE_TRANSFER_BIT, vk.DEPENDENCY_BY_REGION_BIT, nil, nil, []vk.ImageMemoryBarrier{b})
+		// Blit to this mipmap level.
+		blit := vk.BuildImageBlit(0, 0, 0, 0, w, h, nw, nh, i-1, i)
+		vk.CmdBlitImage(cmdBuf, t.img, vk.IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL, t.img, vk.IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL, []vk.ImageBlit{blit}, vk.FILTER_LINEAR)
+		w, h = nw, nh
+	}
+	if t.mipmaps > 1 {
+		// Add barrier for last blit.
+		b := vk.BuildImageMemoryBarrier(
+			t.img,
+			vk.ACCESS_TRANSFER_WRITE_BIT, vk.ACCESS_TRANSFER_READ_BIT,
+			vk.IMAGE_LAYOUT_TRANSFER_DST_OPTIMAL, vk.IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL,
+			t.mipmaps-1, 1,
+		)
+		vk.CmdPipelineBarrier(cmdBuf, vk.PIPELINE_STAGE_TRANSFER_BIT, vk.PIPELINE_STAGE_TRANSFER_BIT, vk.DEPENDENCY_BY_REGION_BIT, nil, nil, []vk.ImageMemoryBarrier{b})
+		t.layout = vk.IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL
+	}
 }
 
 func (t *Texture) Release() {
@@ -756,6 +804,7 @@ func (t *Texture) imageBarrier(cmdBuf vk.CommandBuffer, layout vk.ImageLayout, s
 		t.img,
 		t.scope.access, access,
 		t.layout, layout,
+		0, vk.REMAINING_MIP_LEVELS,
 	)
 	vk.CmdPipelineBarrier(cmdBuf, srcStage, stage, vk.DEPENDENCY_BY_REGION_BIT, nil, nil, []vk.ImageMemoryBarrier{b})
 	t.layout = layout

internal/d3d11/d3d11_windows.go

@@ -685,6 +685,7 @@ const (
 	PRIMITIVE_TOPOLOGY_TRIANGLESTRIP = 5
 
 	FILTER_MIN_MAG_LINEAR_MIP_POINT = 0x14
+	FILTER_MIN_MAG_MIP_LINEAR       = 0x15
 	FILTER_MIN_MAG_MIP_POINT        = 0
 
 	TEXTURE_ADDRESS_MIRROR = 2
@@ -701,6 +702,7 @@ const (
 	BUFFEREX_SRV_FLAG_RAW = 0x1
 
 	RESOURCE_MISC_BUFFER_ALLOW_RAW_VIEWS = 0x20
+	RESOURCE_MISC_GENERATE_MIPS          = 0x1
 
 	CREATE_DEVICE_DEBUG = 0x2
 
@@ -1190,6 +1192,16 @@ func (s *IDXGISwapChain) GetBuffer(index int, riid *GUID) (*IUnknown, error) {
 	return buf, nil
 }
 
+func (c *DeviceContext) GenerateMips(res *ShaderResourceView) {
+	syscall.Syscall(
+		c.Vtbl.GenerateMips,
+		2,
+		uintptr(unsafe.Pointer(c)),
+		uintptr(unsafe.Pointer(res)),
+		0,
+	)
+}
+
 func (c *DeviceContext) Unmap(resource *Resource, subResource uint32) {
 	syscall.Syscall(
 		c.Vtbl.Unmap,

internal/gl/gl.go

@@ -56,6 +56,7 @@ const (
 	GREATER                               = 0x204
 	GEQUAL                                = 0x206
 	LINEAR                                = 0x2601
+	LINEAR_MIPMAP_LINEAR                  = 0x2703
 	LINK_STATUS                           = 0x8b82
 	LUMINANCE                             = 0x1909
 	MAP_READ_BIT                          = 0x0001

internal/gl/gl_js.go

@@ -72,6 +72,7 @@ type Functions struct {
 	_flush                             js.Value
 	_framebufferRenderbuffer           js.Value
 	_framebufferTexture2D              js.Value
+	_generateMipmap                    js.Value
 	_getRenderbufferParameteri         js.Value
 	_getFramebufferAttachmentParameter js.Value
 	_getParameter                      js.Value
@@ -167,6 +168,7 @@ func NewFunctions(ctx Context, forceES bool) (*Functions, error) {
 		_flush:                             _bind(webgl, `flush`),
 		_framebufferRenderbuffer:           _bind(webgl, `framebufferRenderbuffer`),
 		_framebufferTexture2D:              _bind(webgl, `framebufferTexture2D`),
+		_generateMipmap:                    _bind(webgl, `generateMipmap`),
 		_getRenderbufferParameteri:         _bind(webgl, `getRenderbufferParameteri`),
 		_getFramebufferAttachmentParameter: _bind(webgl, `getFramebufferAttachmentParameter`),
 		_getParameter:                      _bind(webgl, `getParameter`),
@@ -419,6 +421,9 @@ func (f *Functions) FramebufferRenderbuffer(target, attachment, renderbuffertarg
 func (f *Functions) FramebufferTexture2D(target, attachment, texTarget Enum, t Texture, level int) {
 	f._framebufferTexture2D.Invoke(int(target), int(attachment), int(texTarget), js.Value(t), level)
 }
+func (f *Functions) GenerateMipmap(target Enum) {
+	f._generateMipmap.Invoke(int(target))
+}
 func (f *Functions) GetError() Enum {
 	// Avoid slow getError calls. See gio#179.
 	return 0

internal/gl/gl_unix.go

@@ -72,6 +72,7 @@ typedef void (*_glFlush)(void);
 typedef void (*_glFramebufferRenderbuffer)(GLenum target, GLenum attachment, GLenum renderbuffertarget, GLuint renderbuffer);
 typedef void (*_glFramebufferTexture2D)(GLenum target, GLenum attachment, GLenum textarget, GLuint texture, GLint level);
 typedef void (*_glGenBuffers)(GLsizei n, GLuint *buffers);
+typedef void (*_glGenerateMipmap)(GLenum target);
 typedef void (*_glGenFramebuffers)(GLsizei n, GLuint *framebuffers);
 typedef void (*_glGenRenderbuffers)(GLsizei n, GLuint *renderbuffers);
 typedef void (*_glGenTextures)(GLsizei n, GLuint *textures);
@@ -286,6 +287,10 @@ static void glGenBuffers(_glGenBuffers f, GLsizei n, GLuint *buffers) {
 	f(n, buffers);
 }
 
+static void glGenerateMipmap(_glGenerateMipmap f, GLenum target) {
+	f(target);
+}
+
 static void glGenFramebuffers(_glGenFramebuffers f, GLsizei n, GLuint *framebuffers) {
 	f(n, framebuffers);
 }
@@ -561,6 +566,7 @@ type Functions struct {
 	glFramebufferRenderbuffer             C._glFramebufferRenderbuffer
 	glFramebufferTexture2D                C._glFramebufferTexture2D
 	glGenBuffers                          C._glGenBuffers
+	glGenerateMipmap                      C._glGenerateMipmap
 	glGenFramebuffers                     C._glGenFramebuffers
 	glGenRenderbuffers                    C._glGenRenderbuffers
 	glGenTextures                         C._glGenTextures
@@ -723,6 +729,7 @@ func (f *Functions) load(forceES bool) error {
 	f.glFramebufferRenderbuffer = must("glFramebufferRenderbuffer")
 	f.glFramebufferTexture2D = must("glFramebufferTexture2D")
 	f.glGenBuffers = must("glGenBuffers")
+	f.glGenerateMipmap = must("glGenerateMipmap")
 	f.glGenFramebuffers = must("glGenFramebuffers")
 	f.glGenRenderbuffers = must("glGenRenderbuffers")
 	f.glGenTextures = must("glGenTextures")
@@ -1048,6 +1055,10 @@ func (f *Functions) FramebufferTexture2D(target, attachment, texTarget Enum, t T
 	C.glFramebufferTexture2D(f.glFramebufferTexture2D, C.GLenum(target), C.GLenum(attachment), C.GLenum(texTarget), C.GLuint(t.V), C.GLint(level))
 }
 
+func (f *Functions) GenerateMipmap(target Enum) {
+	C.glGenerateMipmap(f.glGenerateMipmap, C.GLenum(target))
+}
+
 func (c *Functions) GetBinding(pname Enum) Object {
 	return Object{uint(c.GetInteger(pname))}
 }

internal/gl/gl_windows.go

@@ -35,6 +35,7 @@ var (
 	_glDeleteVertexArrays                  = LibGLESv2.NewProc("glDeleteVertexArrays")
 	_glCompileShader                       = LibGLESv2.NewProc("glCompileShader")
 	_glCopyTexSubImage2D                   = LibGLESv2.NewProc("glCopyTexSubImage2D")
+	_glGenerateMipmap                      = LibGLESv2.NewProc("glGenerateMipmap")
 	_glGenBuffers                          = LibGLESv2.NewProc("glGenBuffers")
 	_glGenFramebuffers                     = LibGLESv2.NewProc("glGenFramebuffers")
 	_glGenVertexArrays                     = LibGLESv2.NewProc("glGenVertexArrays")
@@ -192,6 +193,9 @@ func (c *Functions) CompileShader(s Shader) {
 func (f *Functions) CopyTexSubImage2D(target Enum, level, xoffset, yoffset, x, y, width, height int) {
 	syscall.Syscall9(_glCopyTexSubImage2D.Addr(), 8, uintptr(target), uintptr(level), uintptr(xoffset), uintptr(yoffset), uintptr(x), uintptr(y), uintptr(width), uintptr(height), 0)
 }
+func (f *Functions) GenerateMipmap(target Enum) {
+	syscall.Syscall(_glGenerateMipmap.Addr(), 1, uintptr(target), 0, 0)
+}
 func (c *Functions) CreateBuffer() Buffer {
 	var buf uintptr
 	syscall.Syscall(_glGenBuffers.Addr(), 2, 1, uintptr(unsafe.Pointer(&buf)), 0)

internal/vk/vulkan.go

@@ -303,6 +303,10 @@ static VkResult vkResetDescriptorPool(PFN_vkResetDescriptorPool f, VkDevice devi
 	return f(device, descriptorPool, flags);
 }
 
+static void vkCmdBlitImage(PFN_vkCmdBlitImage f, VkCommandBuffer commandBuffer, VkImage srcImage, VkImageLayout srcImageLayout, VkImage dstImage, VkImageLayout dstImageLayout, uint32_t regionCount, const VkImageBlit* pRegions, VkFilter filter) {
+	f(commandBuffer, srcImage, srcImageLayout, dstImage, dstImageLayout, regionCount, pRegions, filter);
+}
+
 static void vkCmdCopyImage(PFN_vkCmdCopyImage f, VkCommandBuffer commandBuffer, VkImage srcImage, VkImageLayout srcImageLayout, VkImage dstImage, VkImageLayout dstImageLayout, uint32_t regionCount, const VkImageCopy *pRegions) {
 	f(commandBuffer, srcImage, srcImageLayout, dstImage, dstImageLayout, regionCount, pRegions);
 }
@@ -415,6 +419,7 @@ type (
 	Queue                 = C.VkQueue
 	IndexType             = C.VkIndexType
 	Image                 = C.VkImage
+	ImageBlit             = C.VkImageBlit
 	ImageCopy             = C.VkImageCopy
 	ImageLayout           = C.VkImageLayout
 	ImageMemoryBarrier    = C.VkImageMemoryBarrier
@@ -482,9 +487,10 @@ const (
 	FORMAT_R32G32B32_SFLOAT    Format = C.VK_FORMAT_R32G32B32_SFLOAT
 	FORMAT_R32G32B32A32_SFLOAT Format = C.VK_FORMAT_R32G32B32A32_SFLOAT
 
-	FORMAT_FEATURE_COLOR_ATTACHMENT_BIT       FormatFeatureFlags = C.VK_FORMAT_FEATURE_COLOR_ATTACHMENT_BIT
+	FORMAT_FEATURE_COLOR_ATTACHMENT_BIT            FormatFeatureFlags = C.VK_FORMAT_FEATURE_COLOR_ATTACHMENT_BIT
-	FORMAT_FEATURE_COLOR_ATTACHMENT_BLEND_BIT FormatFeatureFlags = C.VK_FORMAT_FEATURE_COLOR_ATTACHMENT_BLEND_BIT
+	FORMAT_FEATURE_COLOR_ATTACHMENT_BLEND_BIT      FormatFeatureFlags = C.VK_FORMAT_FEATURE_COLOR_ATTACHMENT_BLEND_BIT
-	FORMAT_FEATURE_SAMPLED_IMAGE_BIT          FormatFeatureFlags = C.VK_FORMAT_FEATURE_SAMPLED_IMAGE_BIT
+	FORMAT_FEATURE_SAMPLED_IMAGE_BIT               FormatFeatureFlags = C.VK_FORMAT_FEATURE_SAMPLED_IMAGE_BIT
+	FORMAT_FEATURE_SAMPLED_IMAGE_FILTER_LINEAR_BIT FormatFeatureFlags = C.VK_FORMAT_FEATURE_SAMPLED_IMAGE_FILTER_LINEAR_BIT
 
 	IMAGE_USAGE_SAMPLED_BIT          ImageUsageFlags = C.VK_IMAGE_USAGE_SAMPLED_BIT
 	IMAGE_USAGE_COLOR_ATTACHMENT_BIT ImageUsageFlags = C.VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT
@@ -574,6 +580,11 @@ const (
 
 	QUEUE_GRAPHICS_BIT QueueFlags = C.VK_QUEUE_GRAPHICS_BIT
 	QUEUE_COMPUTE_BIT  QueueFlags = C.VK_QUEUE_COMPUTE_BIT
+
+	SAMPLER_MIPMAP_MODE_NEAREST SamplerMipmapMode = C.VK_SAMPLER_MIPMAP_MODE_NEAREST
+	SAMPLER_MIPMAP_MODE_LINEAR  SamplerMipmapMode = C.VK_SAMPLER_MIPMAP_MODE_LINEAR
+
+	REMAINING_MIP_LEVELS = -1
 )
 
 var (
@@ -654,6 +665,7 @@ var funcs struct {
 	vkFreeDescriptorSets                     C.PFN_vkFreeDescriptorSets
 	vkUpdateDescriptorSets                   C.PFN_vkUpdateDescriptorSets
 	vkResetDescriptorPool                    C.PFN_vkResetDescriptorPool
+	vkCmdBlitImage                           C.PFN_vkCmdBlitImage
 	vkCmdCopyImage                           C.PFN_vkCmdCopyImage
 	vkCreateComputePipelines                 C.PFN_vkCreateComputePipelines
 	vkCreateFence                            C.PFN_vkCreateFence
@@ -794,6 +806,7 @@ func vkInit() error {
 		funcs.vkFreeDescriptorSets = must("vkFreeDescriptorSets")
 		funcs.vkUpdateDescriptorSets = must("vkUpdateDescriptorSets")
 		funcs.vkResetDescriptorPool = must("vkResetDescriptorPool")
+		funcs.vkCmdBlitImage = must("vkCmdBlitImage")
 		funcs.vkCmdCopyImage = must("vkCmdCopyImage")
 		funcs.vkCreateComputePipelines = must("vkCreateComputePipelines")
 		funcs.vkCreateFence = must("vkCreateFence")
@@ -1376,6 +1389,13 @@ func CmdBindDescriptorSets(cmdBuf CommandBuffer, point PipelineBindPoint, layout
 	C.vkCmdBindDescriptorSets(funcs.vkCmdBindDescriptorSets, cmdBuf, point, layout, C.uint32_t(firstSet), C.uint32_t(len(sets)), &sets[0], 0, nil)
 }
 
+func CmdBlitImage(cmdBuf CommandBuffer, src Image, srcLayout ImageLayout, dst Image, dstLayout ImageLayout, regions []ImageBlit, filter Filter) {
+	if len(regions) == 0 {
+		return
+	}
+	C.vkCmdBlitImage(funcs.vkCmdBlitImage, cmdBuf, src, srcLayout, dst, dstLayout, C.uint32_t(len(regions)), &regions[0], filter)
+}
+
 func CmdCopyImage(cmdBuf CommandBuffer, src Image, srcLayout ImageLayout, dst Image, dstLayout ImageLayout, regions []ImageCopy) {
 	if len(regions) == 0 {
 		return
@@ -1394,7 +1414,7 @@ func CmdDispatch(cmdBuf CommandBuffer, x, y, z int) {
 	C.vkCmdDispatch(funcs.vkCmdDispatch, cmdBuf, C.uint32_t(x), C.uint32_t(y), C.uint32_t(z))
 }
 
-func CreateImage(pd PhysicalDevice, d Device, format Format, width, height int, usage ImageUsageFlags) (Image, DeviceMemory, error) {
+func CreateImage(pd PhysicalDevice, d Device, format Format, width, height, mipmaps int, usage ImageUsageFlags) (Image, DeviceMemory, error) {
 	inf := C.VkImageCreateInfo{
 		sType:     C.VK_STRUCTURE_TYPE_IMAGE_CREATE_INFO,
 		imageType: C.VK_IMAGE_TYPE_2D,
@@ -1404,7 +1424,7 @@ func CreateImage(pd PhysicalDevice, d Device, format Format, width, height int,
 			height: C.uint32_t(height),
 			depth:  1,
 		},
-		mipLevels:     1,
+		mipLevels:     C.uint32_t(mipmaps),
 		arrayLayers:   1,
 		samples:       C.VK_SAMPLE_COUNT_1_BIT,
 		tiling:        C.VK_IMAGE_TILING_OPTIMAL,
@@ -1451,11 +1471,13 @@ func FreeMemory(d Device, mem DeviceMemory) {
 	C.vkFreeMemory(funcs.vkFreeMemory, d, mem, nil)
 }
 
-func CreateSampler(d Device, minFilter, magFilter Filter) (Sampler, error) {
+func CreateSampler(d Device, minFilter, magFilter Filter, mipmapMode SamplerMipmapMode) (Sampler, error) {
 	inf := C.VkSamplerCreateInfo{
 		sType:        C.VK_STRUCTURE_TYPE_SAMPLER_CREATE_INFO,
 		minFilter:    minFilter,
 		magFilter:    magFilter,
+		mipmapMode:   mipmapMode,
+		maxLod:       C.VK_LOD_CLAMP_NONE,
 		addressModeU: C.VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_EDGE,
 		addressModeV: C.VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_EDGE,
 	}
@@ -1905,7 +1927,7 @@ func BuildViewport(x, y, width, height float32) Viewport {
 	}
 }
 
-func BuildImageMemoryBarrier(img Image, srcMask, dstMask AccessFlags, oldLayout, newLayout ImageLayout) ImageMemoryBarrier {
+func BuildImageMemoryBarrier(img Image, srcMask, dstMask AccessFlags, oldLayout, newLayout ImageLayout, baseMip, numMips int) ImageMemoryBarrier {
 	return C.VkImageMemoryBarrier{
 		sType:         C.VK_STRUCTURE_TYPE_IMAGE_MEMORY_BARRIER,
 		srcAccessMask: srcMask,
@@ -1914,9 +1936,10 @@ func BuildImageMemoryBarrier(img Image, srcMask, dstMask AccessFlags, oldLayout,
 		newLayout:     newLayout,
 		image:         img,
 		subresourceRange: C.VkImageSubresourceRange{
-			aspectMask: C.VK_IMAGE_ASPECT_COLOR_BIT,
+			aspectMask:   C.VK_IMAGE_ASPECT_COLOR_BIT,
-			levelCount: C.VK_REMAINING_MIP_LEVELS,
+			baseMipLevel: C.uint32_t(baseMip),
-			layerCount: C.VK_REMAINING_ARRAY_LAYERS,
+			levelCount:   C.uint32_t(numMips),
+			layerCount:   C.VK_REMAINING_ARRAY_LAYERS,
 		},
 	}
 }
@@ -1982,6 +2005,29 @@ func BuildImageCopy(srcX, srcY, dstX, dstY, width, height int) ImageCopy {
 	}
 }
 
+func BuildImageBlit(srcX, srcY, dstX, dstY, srcWidth, srcHeight, dstWidth, dstHeight, srcMip, dstMip int) ImageBlit {
+	return C.VkImageBlit{
+		srcOffsets: [2]C.VkOffset3D{
+			{C.int32_t(srcX), C.int32_t(srcY), 0},
+			{C.int32_t(srcWidth), C.int32_t(srcHeight), 1},
+		},
+		srcSubresource: C.VkImageSubresourceLayers{
+			aspectMask: C.VK_IMAGE_ASPECT_COLOR_BIT,
+			layerCount: 1,
+			mipLevel:   C.uint32_t(srcMip),
+		},
+		dstOffsets: [2]C.VkOffset3D{
+			{C.int32_t(dstX), C.int32_t(dstY), 0},
+			{C.int32_t(dstWidth), C.int32_t(dstHeight), 1},
+		},
+		dstSubresource: C.VkImageSubresourceLayers{
+			aspectMask: C.VK_IMAGE_ASPECT_COLOR_BIT,
+			layerCount: 1,
+			mipLevel:   C.uint32_t(dstMip),
+		},
+	}
+}
+
 func findMemoryTypeIndex(pd C.VkPhysicalDevice, constraints C.uint32_t, wantProps C.VkMemoryPropertyFlags) (int, bool) {
 	var memProps C.VkPhysicalDeviceMemoryProperties
 	C.vkGetPhysicalDeviceMemoryProperties(funcs.vkGetPhysicalDeviceMemoryProperties, pd, &memProps)