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Thread: Pixelwise occlusion detection in Opengl

  1. #1
    Newbie Newbie
    Join Date
    Sep 2018
    Posts
    1

    Pixelwise occlusion detection in Opengl

    Hi,

    My problem is that I have a triangle mesh and a camera position.
    I would like to draw the triangle indices onto a image rendered by the camera position, therefore I got an image with each pixel indicate the visible triangle index.
    I know how to do this in CPU with a bounding volume hierarchy, e.g. cast a ray for each pixel of the camera and intersect with the triangle mesh, but this is too slow for my application.

    So an intuitive idea is to do this in an offscreen rendering. But I have no idea how to add triangle indices into vertex buffer and have no idea how to draw the indices onto the frame buffer with the indices.

    Is it possible to do in opengl? If possible, please enlighten me a little how to do it?

    Thanks,

    Han

  2. #2
    Senior Member OpenGL Guru
    Join Date
    Jun 2013
    Posts
    2,926
    Create a framebuffer object with an integer-format (e.g. GL_R32I) texture for the colour buffer. The vertex shader only needs to set gl_Position. The fragment shader is just e.g.
    Code :
    out int output;
    void main() {
        output  = gl_PrimitiveID;
    }

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