ebiten/internal/opengl/rendertarget.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 opengl
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import (
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"errors"
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"fmt"
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"github.com/go-gl/gl"
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)
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func orthoProjectionMatrix(left, right, bottom, top int) [4][4]float64 {
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)
return [4][4]float64{
{e11, 0, 0, e14},
{0, e22, 0, e24},
{0, 0, 1, 0},
{0, 0, 0, 1},
}
}
type RenderTarget struct {
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framebuffer gl.Framebuffer
width int
height int
flipY bool
}
func NewRenderTarget(width, height int, flipY bool) *RenderTarget {
return &RenderTarget{
width: width,
height: height,
flipY: flipY,
}
}
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func NewRenderTargetFromTexture(texture *Texture) (*RenderTarget, error) {
framebuffer, err := createFramebuffer(texture.Native())
if err != nil {
return nil, err
}
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return &RenderTarget{
framebuffer: framebuffer,
width: texture.Width(),
height: texture.Height(),
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}, nil
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}
func (r *RenderTarget) Width() int {
return r.width
}
func (r *RenderTarget) Height() int {
return r.height
}
func (r *RenderTarget) FlipY() bool {
return r.flipY
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}
func (r *RenderTarget) Dispose() {
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r.framebuffer.Delete()
}
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func createFramebuffer(nativeTexture gl.Texture) (gl.Framebuffer, error) {
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framebuffer := gl.GenFramebuffer()
framebuffer.Bind()
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gl.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, nativeTexture, 0)
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if gl.CheckFramebufferStatus(gl.FRAMEBUFFER) != gl.FRAMEBUFFER_COMPLETE {
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return 0, errors.New("creating framebuffer failed")
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}
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// Set this framebuffer opaque because alpha values on a target might be
// confusing.
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gl.ClearColor(0, 0, 0, 1)
gl.Clear(gl.COLOR_BUFFER_BIT)
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return framebuffer, nil
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}
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func (r *RenderTarget) SetAsViewport() error {
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gl.Flush()
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r.framebuffer.Bind()
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err := gl.CheckFramebufferStatus(gl.FRAMEBUFFER)
if err != gl.FRAMEBUFFER_COMPLETE {
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return errors.New(fmt.Sprintf("glBindFramebuffer failed: %d", err))
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}
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gl.BlendFuncSeparate(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA, gl.ZERO, gl.ONE)
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width := AdjustSizeForTexture(r.width)
height := AdjustSizeForTexture(r.height)
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gl.Viewport(0, 0, width, height)
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return nil
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}
func (r *RenderTarget) ProjectionMatrix() [4][4]float64 {
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width := AdjustSizeForTexture(r.width)
height := AdjustSizeForTexture(r.height)
m := orthoProjectionMatrix(0, width, 0, height)
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if r.flipY {
m[1][1] *= -1
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m[1][3] += float64(r.height) / float64(AdjustSizeForTexture(r.height)) * 2
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}
return m
}