I'm Using OpenGl ES 1.0 for My Android Game Development, I Want to Draw Dashed-lines Now Im Using This Code to Draw My Line:
gl.glColor4f(1.0f, 0.0f, 0.0f, 1.0f); // gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA); gl.glLineWidth(4.0f); gl.glVertexPointer(2, GL10.GL_FLOAT, 0, mBufDestVertices); gl.glDrawArrays(GL10.GL_LINE_LOOP, 0, mDesPoly.getNumPoints()); How Should I Change It? Does I have to Texture The line? And if so, How?
I recommend to use a 1D texture (performance: use alpha testing instead of blending)
don't forget to:
GL_NEARESTGL_REPEAT
In OpenGL ES 1.0 glLineStipple is not supported. 1 dimensional textures are not supported, too. But 2 dimensional texturing is supported and the Alpha test is supported. See OpenGL ES 1.0 Specification.
A 1 dimensional textures, can be represented by a 2 dimensional Nx1 texture.
The stipple pattern can be encoded in a texture. Create 2 dimensional 4x1 texture with the internal format GL_ALPHA and the following pattern:
1 0 0 1 The minifying and magnification function is GL_NEAREST. The wrap parameters are GL_REPEAT (that is default).
byte arr[] = new byte[] { 255, 0, 0, 255 }; ByteBuffer textureBuffer = ByteBuffer.wrap(arr); gl.glGenTextures(1, texture_id_, stippleTexObj); gl.glBindTexture(GL10.GL_TEXTURE_2D, stippleTexObj); gl.glTexParameteri(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_NEAREST); gl.glTexParameteri(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_NEAREST); gl.glTexParameteri(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_REPEAT); gl.glTexParameteri(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_REPEAT); gl.glTexImage2D(GL10.GL_TEXTURE_2D, 0, GL10.GL_ALPHA, 4, 1, 0, GL10.GL_ALPHA, GL10.GL_UNSIGNED_BYTE, textureBuffer); When you draw the lines, the you have to enable the Alpha test and enable 2 dimensional texturing.
gl.glAlphaFunc(GL10.GL_GEQUAL, 0.5f); gl.glEnable(GL10.GL_ALPHA_TEST); gl.glEnable(GL10.GL_TEXTURE_2D); Ensure that the texture coordinates which are associated to the vertices are aligned to integral values when you draw the line, that causes the the lines start and end with a dash:
e.g. a quad with bottom left of (-0.5 -0.5) and to right of (0.5, 0.5) and the texture coordinates in range [0, 5]:
x y u -0.5f -0.5f 0.0f 0.5f -0.5f 5.0f 0.5f 0.5f 0.0f -0.5f 0.5f 5.0f Since the wrap function is GL_REPEAT and the texture coordinates are in range [0, 5], 5 repetitions of the stipple pattern are wrapped to each edge of the quad.
