ebiten/internal/graphicscommand/shader.go

// Copyright 2020 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package graphicscommand

import (
	"bytes"
	"fmt"
	"go/parser"
	"go/token"
	"strings"

	"github.com/hajimehoshi/ebiten/v2/internal/graphics"
	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
	"github.com/hajimehoshi/ebiten/v2/internal/shader"
	"github.com/hajimehoshi/ebiten/v2/internal/shaderir"
)

var shaderSuffix string

func init() {
	shaderSuffix = `
var __imageDstTextureSize vec2

// imageSrcTextureSize returns the destination image's texture size in pixels.
func imageDstTextureSize() vec2 {
	return __imageDstTextureSize
}
`

	shaderSuffix += fmt.Sprintf(`
var __textureSizes [%[1]d]vec2

// imageSrcTextureSize returns the source image's texture size in pixels.
// As an image is a part of internal texture, the texture is usually bigger than the image.
// The texture's size is useful when you want to calculate pixels from texels.
func imageSrcTextureSize() vec2 {
	return __textureSizes[0]
}

// The unit is the source texture's texel.
var __textureDestinationRegionOrigin vec2

// The unit is the source texture's texel.
var __textureDestinationRegionSize vec2

// imageDstRegionOnTexture returns the destination image's region (the origin and the size) on its texture.
// The unit is the source texture's texel.
//
// As an image is a part of internal texture, the image can be located at an arbitrary position on the texture.
func imageDstRegionOnTexture() (vec2, vec2) {
	return __textureDestinationRegionOrigin, __textureDestinationRegionSize
}

// The unit is the source texture's texel.
var __textureSourceOffsets [%[2]d]vec2

// The unit is the source texture's texel.
var __textureSourceRegionOrigin vec2

// The unit is the source texture's texel.
var __textureSourceRegionSize vec2

// imageSrcRegionOnTexture returns the source image's region (the origin and the size) on its texture.
// The unit is the source texture's texel.
//
// As an image is a part of internal texture, the image can be located at an arbitrary position on the texture.
func imageSrcRegionOnTexture() (vec2, vec2) {
	return __textureSourceRegionOrigin, __textureSourceRegionSize
}
`, graphics.ShaderImageNum, graphics.ShaderImageNum-1)

	for i := 0; i < graphics.ShaderImageNum; i++ {
		pos := "pos"
		if i >= 1 {
			// Convert the position in texture0's texels to the target texture texels.
			pos = fmt.Sprintf("(pos + __textureSourceOffsets[%d]) * __textureSizes[0] / __textureSizes[%d]", i-1, i)
		}
		// __t%d is a special variable for a texture variable.
		shaderSuffix += fmt.Sprintf(`
func imageSrc%[1]dUnsafeAt(pos vec2) vec4 {
	// pos is the position in texels of the source texture (= 0th image's texture).
	return texture2D(__t%[1]d, %[2]s)
}

func imageSrc%[1]dAt(pos vec2) vec4 {
	// pos is the position in texels of the source texture (= 0th image's texture).
	return texture2D(__t%[1]d, %[2]s) *
		step(__textureSourceRegionOrigin.x, pos.x) *
		(1 - step(__textureSourceRegionOrigin.x + __textureSourceRegionSize.x, pos.x)) *
		step(__textureSourceRegionOrigin.y, pos.y) *
		(1 - step(__textureSourceRegionOrigin.y + __textureSourceRegionSize.y, pos.y))
}
`, i, pos)
	}
}

func compileShader(src []byte) (*shaderir.Program, error) {
	var buf bytes.Buffer
	buf.Write(src)
	buf.WriteString(shaderSuffix)
	buf.WriteString(`var __projectionMatrix mat4

func __vertex(position vec2, texCoord vec2, color vec4) (vec4, vec2, vec4) {
	return __projectionMatrix * vec4(position, 0, 1), texCoord, color
}
`)

	fs := token.NewFileSet()
	f, err := parser.ParseFile(fs, "", buf.Bytes(), parser.AllErrors)
	if err != nil {
		return nil, err
	}

	const (
		vert = "__vertex"
		frag = "Fragment"
	)
	ir, err := shader.Compile(fs, f, vert, frag, graphics.ShaderImageNum)
	if err != nil {
		return nil, err
	}

	if ir.VertexFunc.Block == nil {
		return nil, fmt.Errorf("graphicscommand: vertex shader entry point '%s' is missing", vert)
	}
	if ir.FragmentFunc.Block == nil {
		return nil, fmt.Errorf("graphicscommand: fragment shader entry point '%s' is missing", frag)
	}

	return ir, nil
}

type Shader struct {
	shader graphicsdriver.Shader

	uniformNames       []string
	uniformTypes       []shaderir.Type
	uniformNameToIndex map[string]int
	uniformNameToType  map[string]shaderir.Type
}

func NewShader(src []byte) *Shader {
	s := &Shader{}
	c := &newShaderCommand{
		result: s,
		src:    src,
	}
	theCommandQueue.Enqueue(c)
	return s
}

func (s *Shader) Dispose() {
	c := &disposeShaderCommand{
		target: s,
	}
	theCommandQueue.Enqueue(c)
}

func (s *Shader) convertUniforms(uniforms map[string][]float32) [][]float32 {
	if s.shader == nil {
		panic("graphicscommand: shader is not compiled yet")
	}

	if s.uniformNameToIndex == nil {
		s.uniformNameToIndex = map[string]int{}
		s.uniformNameToType = map[string]shaderir.Type{}

		var idx int
		for i, n := range s.uniformNames {
			if strings.HasPrefix(n, "__") {
				continue
			}
			s.uniformNameToIndex[n] = idx
			s.uniformNameToType[n] = s.uniformTypes[i]
			idx++
		}
	}

	us := make([][]float32, len(s.uniformNameToIndex))
	for name, idx := range s.uniformNameToIndex {
		if v, ok := uniforms[name]; ok {
			us[idx] = v
			continue
		}
		t := s.uniformNameToType[name]
		us[idx] = make([]float32, t.FloatNum())
	}

	// TODO: Panic if uniforms include an invalid name

	return us
}