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https://github.com/hajimehoshi/ebiten.git
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33 lines
1.1 KiB
Go
33 lines
1.1 KiB
Go
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// Copyright 2018 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 opengl
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// OrthoProjectionMatrix returns an orthogonal projection matrix for OpenGL.
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//
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// The matrix converts the coodinates (left, bottom) - (right, top) to the normalized device coodinates (-1, -1) - (1, 1).
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func OrthoProjectionMatrix(left, right, bottom, top int) []float32 {
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e11 := 2 / float32(right-left)
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e22 := 2 / float32(top-bottom)
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e14 := -1 * float32(right+left) / float32(right-left)
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e24 := -1 * float32(top+bottom) / float32(top-bottom)
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return []float32{
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e11, 0, 0, 0,
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0, e22, 0, 0,
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0, 0, 1, 0,
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e14, e24, 0, 1,
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}
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}
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