147 lines
4.1 KiB
Go
147 lines
4.1 KiB
Go
// Ported from GLUT's samples. Original copyright below applies.
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/* Copyright (c) Mark J. Kilgard, 1996. */
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/* This program is freely distributable without licensing fees
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and is provided without guarantee or warrantee expressed or
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implied. This program is -not- in the public domain. */
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/* This program is a response to a question posed by Gil Colgate
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<gcolgate@sirius.com> about how lengthy a program is required using
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OpenGL compared to using Direct3D immediate mode to "draw a
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triangle at screen coordinates 0,0, to 200,200 to 20,200, and I
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want it to be blue at the top vertex, red at the left vertex, and
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green at the right vertex". I'm not sure how long the Direct3D
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program is; Gil has used Direct3D and his guess is "about 3000
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lines of code". */
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package main
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import (
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"gl"
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"glut"
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"exp/draw"
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"image"
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"freetype-go.googlecode.com/hg/freetype/raster"
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"draw2d.googlecode.com/svn/trunk/draw2d/src/pkg/draw2d"
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"postscript-go.googlecode.com/svn/trunk/postscript-go/src/pkg/postscript"
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"fmt"
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)
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type GLPainter struct {
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// The Porter-Duff composition operator.
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Op draw.Op
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// The 16-bit color to paint the spans.
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cr, cg, cb uint8
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ca uint32
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}
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const M16 uint32 = 1<<16 - 1
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const M32 uint32 = 1<<32 - 1
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// Paint satisfies the Painter interface by painting ss onto an image.RGBA.
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func (p *GLPainter) Paint(ss []raster.Span, done bool) {
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gl.Begin(gl.LINES)
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for _, s := range ss {
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ma := s.A >> 16
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a := ma * p.ca / M16
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gl.Color4ub(p.cr, p.cg, p.cb, uint8(a>>8))
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gl.Vertex2i(s.X0, s.Y)
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gl.Vertex2i(s.X1, s.Y)
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}
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gl.End()
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}
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// SetColor sets the color to paint the spans.
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func (p *GLPainter) SetColor(c image.Color) {
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r, g, b, a := c.RGBA()
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if a == 0 {
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p.cr = 0
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p.cg = 0
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p.cb = 0
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p.ca = a
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} else {
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p.cr = uint8((r * M16 / a) >> 8)
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p.cg = uint8((g * M16 / a) >> 8)
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p.cb = uint8((b * M16 / a) >> 8)
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p.ca = a
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}
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}
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// NewRGBAPainter creates a new RGBAPainter for the given image.
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func NewGLPainter() *GLPainter {
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return &GLPainter{}
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}
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func TestDrawCubicCurve(gc draw2d.GraphicContext) {
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// draw a cubic curve
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x, y := 25.6, 128.0
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x1, y1 := 102.4, 230.4
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x2, y2 := 153.6, 25.6
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x3, y3 := 230.4, 128.0
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gc.SetStrokeColor(image.NRGBAColor{0, 0, 0, 0xff})
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gc.SetLineWidth(10)
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gc.MoveTo(x, y)
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gc.CubicCurveTo(x1, y1, x2, y2, x3, y3)
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gc.Stroke()
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gc.SetStrokeColor(image.NRGBAColor{0xFF, 0x33, 0x33, 0x99})
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gc.SetLineWidth(6)
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// draw segment of curve
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gc.MoveTo(x, y)
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gc.LineTo(x1, y1)
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gc.MoveTo(x2, y2)
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gc.LineTo(x3, y3)
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gc.Stroke()
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}
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var (
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width, height int
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)
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func reshape(w, h int) {
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/* Because Gil specified "screen coordinates" (presumably with an
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upper-left origin), this short bit of code sets up the coordinate
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system to correspond to actual window coodrinates. This code
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wouldn't be required if you chose a (more typical in 3D) abstract
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coordinate system. */
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gl.ClearColor(1, 1, 1, 1)
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//fmt.Println(gl.GetString(gl.EXTENSIONS))
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gl.Viewport(0, 0, w, h) /* Establish viewing area to cover entire window. */
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gl.MatrixMode(gl.PROJECTION) /* Start modifying the projection matrix. */
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gl.LoadIdentity() /* Reset project matrix. */
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gl.Ortho(0, float64(w), 0, float64(h), -1, 1) /* Map abstract coords directly to window coords. */
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gl.Scalef(1, -1, 1) /* Invert Y axis so increasing Y goes down. */
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gl.Translatef(0, float32(-h), 0) /* Shift origin up to upper-left corner. */
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gl.Enable(gl.BLEND)
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gl.BlendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)
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width, height = w, h
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}
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func display() {
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gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
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gl.LineWidth(1)
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p := NewGLPainter()
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fmt.Println("draw")
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gc := draw2d.NewImageGraphicContextFromPainter(p, image.Rect(0, 0, width, height))
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gc.Translate(0, 380)
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gc.Scale(1, -1)
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gc.Translate(0, -380)
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interpreter := postscript.NewInterpreter(gc)
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interpreter.ExecuteFile("../../tiger.ps")
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gl.Flush() /* Single buffered, so needs a flush. */
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}
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func main() {
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glut.Init()
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glut.InitWindowSize(800, 800)
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glut.CreateWindow("single triangle")
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glut.DisplayFunc(display)
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glut.ReshapeFunc(reshape)
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glut.MainLoop()
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}
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