" gl_Position = uMVPMatrix * vPosition " + If you want to create geometry for the circle, do something like this: int vertexCount = 30 įloat buffer = new float // (x,y) for each vertexįor (int i = 0 i < outerVertexCount ++i) All you need happens within the fragment-shader. Not very complex to implement, so I don't offer any basic rendering code here. You can change this so that it gives you the desired output.Īnd that is it. While (textureCoord.x * textureCoord.x) + (textureCoord.y * textureCoord.y) <= 1.0 is the inequality, because you need a circle, you have to render every pixel within that range, not just the border. Render colored and desired transparency In your fragment-shader, use something like this: if ((textureCoord.x * textureCoord.x) + (textureCoord.y * textureCoord.y) <= 1.0) You need a vertex-buffer for the vertices, an index-buffer for the indices if you're a using a square geometry, and a textureCoord-buffer for your texture coordinates.įor a square I recommend using -1.0 as the lowest and 1.0 as the highest texture coordinate, because then you are able to use the unit circle equation. It needs blending, but this is not really hard to get to work. Rendering at least a triangle or a sqare/quad and use the fragment-shader to only make the disired (based on a equation) pixel visible.
There is another method, which I personally use in every graphics API. Having different circles, styling and colring them is hard to master. For a real circle you need as many vertices as your circle have pixels. If you want to get acceptable accuracy you need a lot of vertices and any of these vertices need to be processed in the shader. I definitely do not recommend rendering a circle through geometry.
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