mirror of
https://github.com/hajimehoshi/ebiten.git
synced 2024-11-10 04:57:26 +01:00
102 lines
3.0 KiB
Go
102 lines
3.0 KiB
Go
// Copyright 2014 Hajime Hoshi
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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 graphics
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import (
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"github.com/hajimehoshi/ebiten/internal/opengl"
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"github.com/hajimehoshi/ebiten/internal/web"
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)
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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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// framebuffer is a wrapper of OpenGL's framebuffer.
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type framebuffer struct {
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native opengl.Framebuffer
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proMatrix []float32
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width int
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height int
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}
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// newFramebufferFromTexture creates a framebuffer from the given texture.
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func newFramebufferFromTexture(texture *texture, width, height int) (*framebuffer, error) {
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native, err := opengl.GetContext().NewFramebuffer(opengl.Texture(texture.native))
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if err != nil {
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return nil, err
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}
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return &framebuffer{
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native: native,
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width: width,
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height: height,
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}, nil
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}
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// newScreenFramebuffer creates a framebuffer for the screen.
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func newScreenFramebuffer(width, height int) *framebuffer {
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return &framebuffer{
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native: opengl.GetContext().ScreenFramebuffer(),
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width: width,
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height: height,
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}
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}
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// viewportSize returns the viewport size of the framebuffer.
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func (f *framebuffer) viewportSize() (int, int) {
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// On some browsers, viewport size must be within the framebuffer size.
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// e.g. Edge (#71), Chrome on GPD Pocket (#420)
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if web.IsBrowser() {
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return f.width, f.height
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}
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// If possible, always use the same viewport size to reduce draw calls.
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m := MaxImageSize()
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return m, m
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}
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// setAsViewport sets the framebuffer as the current viewport.
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func (f *framebuffer) setAsViewport() {
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w, h := f.viewportSize()
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opengl.GetContext().SetViewport(f.native, w, h)
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}
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// projectionMatrix returns a projection matrix of the framebuffer.
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//
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// A projection matrix converts the coodinates on the framebuffer
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// (0, 0) - (viewport width, viewport height)
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// to the normalized device coodinates (-1, -1) - (1, 1) with adjustment.
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func (f *framebuffer) projectionMatrix() []float32 {
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if f.proMatrix != nil {
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return f.proMatrix
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}
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w, h := f.viewportSize()
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m := orthoProjectionMatrix(0, w, 0, h)
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f.proMatrix = m
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return f.proMatrix
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}
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