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go.mobile/gl/glutil: use a triangle strip instead of two triangles. 

It's not a big deal in this case, but we'll probably want to do the same
for the sprite/gl package.

LGTM=crawshaw
R=crawshaw
CC=golang-codereviews
https://golang.org/cl/163990043
This commit is contained in:
Nigel Tao 2014-10-28 10:55:58 +11:00
parent 85b2f78310
commit 3aced57cb0
1 changed files with 21 additions and 28 deletions
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49
gl/glutil/glimage.go
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@ -19,8 +19,8 @@ import (
var glimage struct { var glimage struct {
sync.Once sync.Once
square gl.Buffer quadXY gl.Buffer
squareUV gl.Buffer quadUV gl.Buffer
program gl.Program program gl.Program
pos gl.Attrib pos gl.Attrib
mvp gl.Uniform mvp gl.Uniform
@ -36,13 +36,13 @@ func glInit() {
panic(err) panic(err)
} }
glimage.square = gl.GenBuffer() glimage.quadXY = gl.GenBuffer()
glimage.squareUV = gl.GenBuffer() glimage.quadUV = gl.GenBuffer()
gl.BindBuffer(gl.ARRAY_BUFFER, glimage.square) gl.BindBuffer(gl.ARRAY_BUFFER, glimage.quadXY)
gl.BufferData(gl.ARRAY_BUFFER, gl.STATIC_DRAW, squareCoords) gl.BufferData(gl.ARRAY_BUFFER, gl.STATIC_DRAW, quadXYCoords)
gl.BindBuffer(gl.ARRAY_BUFFER, glimage.squareUV) gl.BindBuffer(gl.ARRAY_BUFFER, glimage.quadUV)
gl.BufferData(gl.ARRAY_BUFFER, gl.STATIC_DRAW, squareUVCoords) gl.BufferData(gl.ARRAY_BUFFER, gl.STATIC_DRAW, quadUVCoords)
glimage.pos = gl.GetAttribLocation(glimage.program, "pos") glimage.pos = gl.GetAttribLocation(glimage.program, "pos")
glimage.mvp = gl.GetUniformLocation(glimage.program, "mvp") glimage.mvp = gl.GetUniformLocation(glimage.program, "mvp")
@ -224,39 +224,32 @@ func (img *Image) Draw(dstBounds geom.Rectangle, srcBounds image.Rectangle) {
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST) gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST)
gl.Uniform1i(glimage.textureSample, 0) gl.Uniform1i(glimage.textureSample, 0)
gl.BindBuffer(gl.ARRAY_BUFFER, glimage.square) gl.BindBuffer(gl.ARRAY_BUFFER, glimage.quadXY)
gl.EnableVertexAttribArray(glimage.pos) gl.EnableVertexAttribArray(glimage.pos)
gl.VertexAttribPointer(glimage.pos, 2, gl.FLOAT, false, 0, 0) gl.VertexAttribPointer(glimage.pos, 2, gl.FLOAT, false, 0, 0)
gl.BindBuffer(gl.ARRAY_BUFFER, glimage.squareUV) gl.BindBuffer(gl.ARRAY_BUFFER, glimage.quadUV)
gl.EnableVertexAttribArray(glimage.inUV) gl.EnableVertexAttribArray(glimage.inUV)
gl.VertexAttribPointer(glimage.inUV, 2, gl.FLOAT, false, 0, 0) gl.VertexAttribPointer(glimage.inUV, 2, gl.FLOAT, false, 0, 0)
gl.DrawArrays(gl.TRIANGLES, 0, 6) gl.DrawArrays(gl.TRIANGLE_STRIP, 0, 4)
gl.DisableVertexAttribArray(glimage.pos) gl.DisableVertexAttribArray(glimage.pos)
gl.DisableVertexAttribArray(glimage.inUV) gl.DisableVertexAttribArray(glimage.inUV)
} }
// Vertices of two triangles. var quadXYCoords = toBytes([]float32{
var squareCoords = toBytes([]float32{ -1, -1, // bottom left
-1, -1, +1, -1, // bottom right
+1, -1, -1, +1, // top left
+1, +1, +1, +1, // top right
-1, -1,
+1, +1,
-1, +1,
}) })
var squareUVCoords = toBytes([]float32{ var quadUVCoords = toBytes([]float32{
0, 1, 0, 1, // bottom left
1, 1, 1, 1, // bottom right
1, 0, 0, 0, // top left
1, 0, // top right
0, 1,
1, 0,
0, 0,
}) })
func toBytes(v []float32) []byte { func toBytes(v []float32) []byte {