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/graphics/opengl"
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)
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func orthoProjectionMatrix(left, right, bottom, top int) *[4][4]float64 {
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e11 := float64(2) / float64(right-left)
e22 := float64(2) / float64(top-bottom)
e14 := -1 * float64(right+left) / float64(right-left)
e24 := -1 * float64(top+bottom) / float64(top-bottom)
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return &[4][4]float64{
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{e11, 0, 0, e14},
{0, e22, 0, e24},
{0, 0, 1, 0},
{0, 0, 0, 1},
}
}
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type framebuffer struct {
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native opengl.Framebuffer
width int
height int
flipY bool
proMatrix *[4][4]float64
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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,
width: texture.width,
height: texture.height,
}, 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() *[4][4]float64 {
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if f.proMatrix != nil {
return f.proMatrix
}
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width := viewportSize
height := viewportSize
m := orthoProjectionMatrix(0, width, 0, height)
if f.flipY {
m[1][1] *= -1
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m[1][3] += float64(f.height) / float64(height) * 2
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}
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f.proMatrix = m
return f.proMatrix
}