ebiten/internal/graphics/vertex.go

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// Copyright 2019 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 graphics
import (
"sync"
)
const (
ShaderImageNum = 4
// PreservedUniformVariablesNum represents the number of preserved uniform variables.
// Any shaders in Ebiten must have these uniform variables.
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PreservedUniformVariablesNum = 1 + // the destination texture size
1 + // the texture sizes array
1 + // the texture destination region's origin
1 + // the texture destination region's size
1 + // the offsets array of the second and the following images
1 + // the texture source region's origin
1 // the texture source region's size
DestinationTextureSizeUniformVariableIndex = 0
TextureSizesUniformVariableIndex = 1
TextureDestinationRegionOriginUniformVariableIndex = 2
TextureDestinationRegionSizeUniformVariableIndex = 3
TextureSourceOffsetsUniformVariableIndex = 4
TextureSourceRegionOriginUniformVariableIndex = 5
TextureSourceRegionSizeUniformVariableIndex = 6
)
const (
IndicesNum = (1 << 16) / 3 * 3 // Adjust num for triangles.
VertexFloatNum = 8
)
var (
quadIndices = []uint16{0, 1, 2, 1, 2, 3}
)
func QuadIndices() []uint16 {
return quadIndices
}
var (
theVerticesBackend = &verticesBackend{}
)
type verticesBackend struct {
backend []float32
head int
m sync.Mutex
}
func (v *verticesBackend) slice(n int) []float32 {
v.m.Lock()
defer v.m.Unlock()
need := n * VertexFloatNum
if v.head+need > len(v.backend) {
v.backend = nil
v.head = 0
}
if v.backend == nil {
l := 1024
if n > l {
l = n
}
v.backend = make([]float32, VertexFloatNum*l)
}
s := v.backend[v.head : v.head+need]
v.head += need
return s
}
// Vertices returns a float32 slice for n vertices.
// Vertices returns a slice that never overlaps with other slices returned this function,
// and users can do optimization based on this fact.
func Vertices(n int) []float32 {
return theVerticesBackend.slice(n)
}
// QuadVertices returns a float32 slice for a quadrangle.
// QuadVertices returns a slice that never overlaps with other slices returned this function,
// and users can do optimization based on this fact.
func QuadVertices(sx0, sy0, sx1, sy1 float32, a, b, c, d, tx, ty float32, cr, cg, cb, ca float32) []float32 {
x := sx1 - sx0
y := sy1 - sy0
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ax, by, cx, dy := a*x, b*y, c*x, d*y
u0, v0, u1, v1 := float32(sx0), float32(sy0), float32(sx1), float32(sy1)
// Use the vertex backend instead of calling make to reduce GCs (#1521).
vs := theVerticesBackend.slice(4)
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// This function is very performance-sensitive and implement in a very dumb way.
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_ = vs[:4*VertexFloatNum]
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vs[0] = tx
vs[1] = ty
vs[2] = u0
vs[3] = v0
vs[4] = cr
vs[5] = cg
vs[6] = cb
vs[7] = ca
vs[8] = ax + tx
vs[9] = cx + ty
vs[10] = u1
vs[11] = v0
vs[12] = cr
vs[13] = cg
vs[14] = cb
vs[15] = ca
vs[16] = by + tx
vs[17] = dy + ty
vs[18] = u0
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vs[19] = v1
vs[20] = cr
vs[21] = cg
vs[22] = cb
vs[23] = ca
vs[24] = ax + by + tx
vs[25] = cx + dy + ty
vs[26] = u1
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vs[27] = v1
vs[28] = cr
vs[29] = cg
vs[30] = cb
vs[31] = ca
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return vs
}