mirror of
https://github.com/hajimehoshi/ebiten.git
synced 2024-09-20 13:22:19 +02:00
122 lines
2.7 KiB
Go
122 lines
2.7 KiB
Go
// Copyright 2017 The Ebiten Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package graphicsutil
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import (
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"github.com/hajimehoshi/ebiten/internal/graphics"
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"github.com/hajimehoshi/ebiten/internal/opengl"
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)
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var (
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theVerticesBackend = &verticesBackend{}
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)
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type verticesBackend struct {
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backend []float32
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head int
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}
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func (v *verticesBackend) sliceForOneQuad() []float32 {
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const num = 256
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size := 4 * graphics.VertexSizeInBytes() / opengl.Float.SizeInBytes()
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if v.backend == nil {
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v.backend = make([]float32, size*num)
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}
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s := v.backend[v.head : v.head+size]
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v.head += size
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if v.head+size > len(v.backend) {
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v.backend = nil
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v.head = 0
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}
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return s
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}
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func isPowerOf2(x int) bool {
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return (x & (x - 1)) == 0
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}
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func QuadVertices(width, height int, sx0, sy0, sx1, sy1 int, a, b, c, d, tx, ty float32) []float32 {
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if !isPowerOf2(width) {
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panic("not reached")
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}
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if !isPowerOf2(height) {
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panic("not reached")
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}
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if sx0 >= sx1 || sy0 >= sy1 {
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return nil
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}
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if sx1 <= 0 || sy1 <= 0 {
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return nil
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}
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wf := float32(width)
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hf := float32(height)
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u0, v0, u1, v1 := float32(sx0)/wf, float32(sy0)/hf, float32(sx1)/wf, float32(sy1)/hf
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return quadVerticesImpl(float32(sx1-sx0), float32(sy1-sy0), u0, v0, u1, v1, a, b, c, d, tx, ty)
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}
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func quadVerticesImpl(x, y, u0, v0, u1, v1, a, b, c, d, tx, ty float32) []float32 {
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// Specifying a range explicitly here is redundant but this helps optimization
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// to eliminate boundry checks.
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vs := theVerticesBackend.sliceForOneQuad()[0:24]
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ax, by, cx, dy := a*x, b*y, c*x, d*y
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// Vertex coordinates
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vs[0] = tx
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vs[1] = ty
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// Texture coordinates: first 2 values indicates the actual coodinate, and
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// the second indicates diagonally opposite coodinates.
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// The second is needed to calculate source rectangle size in shader programs.
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vs[2] = u0
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vs[3] = v0
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vs[4] = u1
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vs[5] = v1
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// and the same for the other three coordinates
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vs[6] = ax + tx
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vs[7] = cx + ty
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vs[8] = u1
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vs[9] = v0
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vs[10] = u0
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vs[11] = v1
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vs[12] = by + tx
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vs[13] = dy + ty
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vs[14] = u0
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vs[15] = v1
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vs[16] = u1
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vs[17] = v0
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vs[18] = ax + by + tx
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vs[19] = cx + dy + ty
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vs[20] = u1
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vs[21] = v1
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vs[22] = u0
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vs[23] = v0
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return vs
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}
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var (
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quadIndices = []uint16{0, 1, 2, 1, 2, 3}
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)
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func QuadIndices() []uint16 {
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return quadIndices
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}
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