ebiten/internal/graphics/vertices.go

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// Copyright 2017 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.
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package graphics
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var (
theVerticesBackend = &verticesBackend{}
)
type verticesBackend struct {
backend []float32
head int
}
const (
IndicesNum = (1 << 16) / 3 * 3 // Adjust num for triangles.
VertexFloatNum = 10
)
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func (v *verticesBackend) slice(n int) []float32 {
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const num = 1024
if n > num {
panic("not reached")
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}
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need := n * VertexFloatNum
if v.head+need > len(v.backend) {
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v.backend = nil
v.head = 0
}
if v.backend == nil {
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v.backend = make([]float32, VertexFloatNum*num)
}
s := v.backend[v.head : v.head+need]
v.head += need
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return s
}
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func isPowerOf2(x int) bool {
if x <= 0 {
return false
}
return (x & (x - 1)) == 0
}
func QuadVertices(width, height int, sx0, sy0, sx1, sy1 int, a, b, c, d, tx, ty float32, cr, cg, cb, ca float32) []float32 {
if !isPowerOf2(width) {
panic("not reached")
}
if !isPowerOf2(height) {
panic("not reached")
}
if sx0 >= sx1 || sy0 >= sy1 {
return nil
}
if sx1 <= 0 || sy1 <= 0 {
return nil
}
wf := float32(width)
hf := float32(height)
u0, v0, u1, v1 := float32(sx0)/wf, float32(sy0)/hf, float32(sx1)/wf, float32(sy1)/hf
return quadVerticesImpl(float32(sx1-sx0), float32(sy1-sy0), u0, v0, u1, v1, a, b, c, d, tx, ty, cr, cg, cb, ca)
}
func quadVerticesImpl(x, y, u0, v0, u1, v1, a, b, c, d, tx, ty, cr, cg, cb, ca float32) []float32 {
// Specifying a range explicitly here is redundant but this helps optimization
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// to eliminate boundary checks.
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//
// 4*VertexFloatNum is better than 40, but in GopherJS, optimization might not work.
vs := theVerticesBackend.slice(4)[0:40]
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ax, by, cx, dy := a*x, b*y, c*x, d*y
// Vertex coordinates
vs[0] = tx
vs[1] = ty
// Texture coordinates: first 2 values indicates the actual coodinate, and
// the second indicates diagonally opposite coodinates.
// The second is needed to calculate source rectangle size in shader programs.
vs[2] = u0
vs[3] = v0
vs[4] = u1
vs[5] = v1
vs[6] = cr
vs[7] = cg
vs[8] = cb
vs[9] = ca
// and the same for the other three coordinates
vs[10] = ax + tx
vs[11] = cx + ty
vs[12] = u1
vs[13] = v0
vs[14] = u0
vs[15] = v1
vs[16] = cr
vs[17] = cg
vs[18] = cb
vs[19] = ca
vs[20] = by + tx
vs[21] = dy + ty
vs[22] = u0
vs[23] = v1
vs[24] = u1
vs[25] = v0
vs[26] = cr
vs[27] = cg
vs[28] = cb
vs[29] = ca
vs[30] = ax + by + tx
vs[31] = cx + dy + ty
vs[32] = u1
vs[33] = v1
vs[34] = u0
vs[35] = v0
vs[36] = cr
vs[37] = cg
vs[38] = cb
vs[39] = ca
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return vs
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}
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var (
quadIndices = []uint16{0, 1, 2, 1, 2, 3}
)
func QuadIndices() []uint16 {
return quadIndices
}
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func PutVertex(vs []float32, width, height int, dx, dy, sx, sy float32, cr, cg, cb, ca float32) {
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if !isPowerOf2(width) {
panic("not reached")
}
if !isPowerOf2(height) {
panic("not reached")
}
wf := float32(width)
hf := float32(height)
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// Specify -1 for the source region, which means the source region is ignored.
//
// NaN would make more sense to represent an invalid state, but vertices including NaN values doesn't work on
// some machines (#696). Let's use negative numbers to represent such state.
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vs[0] = dx
vs[1] = dy
vs[2] = sx / wf
vs[3] = sy / hf
vs[4] = -1
vs[5] = -1
vs[6] = cr
vs[7] = cg
vs[8] = cb
vs[9] = ca
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}