ebiten/internal/shaderir/hlsl/packing.go

107 lines
2.8 KiB
Go

// Copyright 2022 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 hlsl
import (
"fmt"
"github.com/hajimehoshi/ebiten/v2/internal/shaderir"
)
const boundaryInBytes = 16
func CalcUniformMemoryOffsets(program *shaderir.Program) []int {
// https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-packing-rules
// https://github.com/microsoft/DirectXShaderCompiler/wiki/Buffer-Packing
var offsets []int
var head int
align := func(x int) int {
if x == 0 {
return 0
}
return ((x-1)/boundaryInBytes + 1) * boundaryInBytes
}
// TODO: Reorder the variables with packoffset.
// See https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-variable-packoffset
for _, u := range program.Uniforms {
switch u.Main {
case shaderir.Float:
offsets = append(offsets, head)
head += 4
case shaderir.Int:
offsets = append(offsets, head)
head += 4
case shaderir.Vec2, shaderir.IVec2:
if head%boundaryInBytes >= 4*3 {
head = align(head)
}
offsets = append(offsets, head)
head += 4 * 2
case shaderir.Vec3, shaderir.IVec3:
if head%boundaryInBytes >= 4*2 {
head = align(head)
}
offsets = append(offsets, head)
head += 4 * 3
case shaderir.Vec4, shaderir.IVec4:
if head%boundaryInBytes >= 4*1 {
head = align(head)
}
offsets = append(offsets, head)
head += 4 * 4
case shaderir.Mat2:
// For matrices, each column is aligned to the boundary.
head = align(head)
offsets = append(offsets, head)
head += 4 * 6
case shaderir.Mat3:
head = align(head)
offsets = append(offsets, head)
head += 4 * 11
case shaderir.Mat4:
head = align(head)
offsets = append(offsets, head)
head += 4 * 16
case shaderir.Array:
// Each array is 16-byte aligned.
// TODO: What if the array has 2 or more dimensions?
head = align(head)
offsets = append(offsets, head)
n := u.Sub[0].Uint32Count()
switch u.Sub[0].Main {
case shaderir.Mat2:
n = 6
case shaderir.Mat3:
n = 11
case shaderir.Mat4:
n = 16
}
head += (u.Length - 1) * align(4*n)
// The last element is not with a padding.
head += 4 * n
case shaderir.Struct:
// TODO: Implement this
panic("hlsl: offset for a struct is not implemented yet")
default:
panic(fmt.Sprintf("hlsl: unexpected type: %s", u.String()))
}
}
return offsets
}