Generating depth map with panda3d

Question

I need to generate test data for 3d reconstruction code. For this I decided to use panda3d. I am able to create simple app and see the scene. Now I need to create depth map for the scene, i.e. for each pixel on the screen I need to calculate depth, i.e. distance from camera to the closest object in the 3d space (moving perpendicularly to camera plane). What API functions are more suitable for that?

Answer 1

This is in principle similar to shadow mapping, as demonstrated in the advanced shadow sample. You will need to create an offscreen buffer and camera to render the depth buffer. Note that unless you use an orthographic lens, the resulting depth values will not be linear and will need to be transformed to a linear value using the near and far values of the lens. The near and far distances should be configured such as to get the desired range of depth values.

Alternatively, you can use a shader to write the appropriate distance values into the colour buffer, which is particularly useful if you want to store distance values of a perspective camera without having to undo the perspective projection later, or if you want to store the original world-space positions.

If you want to be able to access the values on the CPU, you will need to use the RTM_copy_ram value instead of RTM_bind_or_copy when binding your texture to tell Panda3D to transfer the results of rendering the buffer to CPU-accessible memory.