ebiten/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 ebiten
import (
"sync"
"github.com/hajimehoshi/ebiten/internal/graphics"
)
var (
theVerticesBackend = &verticesBackend{
backend: make([]float32, graphics.VertexFloatNum*1024),
}
)
type verticesBackend struct {
backend []float32
head int
m sync.Mutex
}
func (v *verticesBackend) slice(n int, last bool) []float32 {
v.m.Lock()
need := n * graphics.VertexFloatNum
if l := len(v.backend); v.head+need > l {
for v.head+need > l {
l *= 2
}
v.backend = make([]float32, l)
v.head = 0
}
s := v.backend[v.head : v.head+need]
if last {
// If last is true, the vertices backend is sent to GPU and it is fine to reuse the slice.
v.head = 0
} else {
v.head += need
}
v.m.Unlock()
return s
}
func vertexSlice(n int, last bool) []float32 {
return theVerticesBackend.slice(n, last)
}
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func quadVertices(sx0, sy0, sx1, sy1 int, a, b, c, d, tx, ty float32, cr, cg, cb, ca float32, last bool) []float32 {
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x := float32(sx1 - sx0)
y := float32(sy1 - sy0)
ax, by, cx, dy := a*x, b*y, c*x, d*y
u0, v0, u1, v1 := float32(sx0), float32(sy0), float32(sx1), float32(sy1)
// This function is very performance-sensitive and implement in a very dumb way.
vs := vertexSlice(4, last)
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_ = vs[:48]
// For each values, see the comment at shareable.(*Image).DrawTriangles.
vs[0] = tx
vs[1] = ty
vs[2] = u0
vs[3] = v0
vs[4] = u0
vs[5] = v0
vs[6] = u1
vs[7] = v1
vs[8] = cr
vs[9] = cg
vs[10] = cb
vs[11] = ca
vs[12] = ax + tx
vs[13] = cx + ty
vs[14] = u1
vs[15] = v0
vs[16] = u0
vs[17] = v0
vs[18] = u1
vs[19] = v1
vs[20] = cr
vs[21] = cg
vs[22] = cb
vs[23] = ca
vs[24] = by + tx
vs[25] = dy + ty
vs[26] = u0
vs[27] = v1
vs[28] = u0
vs[29] = v0
vs[30] = u1
vs[31] = v1
vs[32] = cr
vs[33] = cg
vs[34] = cb
vs[35] = ca
vs[36] = ax + by + tx
vs[37] = cx + dy + ty
vs[38] = u1
vs[39] = v1
vs[40] = u0
vs[41] = v0
vs[42] = u1
vs[43] = v1
vs[44] = cr
vs[45] = cg
vs[46] = cb
vs[47] = ca
return vs
}