ebiten/internal/graphics/framebuffer.go

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// Copyright 2014 Hajime Hoshi
//
// 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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import (
"github.com/hajimehoshi/ebiten/internal/opengl"
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)
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func orthoProjectionMatrix(left, right, bottom, top int) []float32 {
e11 := 2 / float32(right-left)
e22 := 2 / float32(top-bottom)
e14 := -1 * float32(right+left) / float32(right-left)
e24 := -1 * float32(top+bottom) / float32(top-bottom)
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return []float32{
e11, 0, 0, 0,
0, e22, 0, 0,
0, 0, 1, 0,
e14, e24, 0, 1,
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}
}
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type framebuffer struct {
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native opengl.Framebuffer
flipY bool
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proMatrix []float32
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}
func newFramebufferFromTexture(context *opengl.Context, texture *texture) (*framebuffer, error) {
native, err := context.NewFramebuffer(opengl.Texture(texture.native))
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if err != nil {
return nil, err
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}
return &framebuffer{
native: native,
}, nil
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}
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const viewportSize = 4096
func (f *framebuffer) setAsViewport(context *opengl.Context) error {
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width := viewportSize
height := viewportSize
return context.SetViewport(f.native, width, height)
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}
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func (f *framebuffer) projectionMatrix(height int) []float32 {
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if f.proMatrix != nil {
return f.proMatrix
}
m := orthoProjectionMatrix(0, viewportSize, 0, viewportSize)
if f.flipY {
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m[4*1+1] *= -1
m[4*3+1] += float32(height) / float32(viewportSize) * 2
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}
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f.proMatrix = m
return f.proMatrix
}