Customizing the rendering range for individual cameras. #2020

LinShuang22 · 2024-03-20T06:34:55Z

LinShuang22
Mar 20, 2024

Hi,

I'm a student and I'm trying to use MuJoCo for simulating cameras.

I'm looking for some help with customizing the rendering range for individual cameras. In my simulation environment, there are many cameras, and each camera requires a different rendering range. I know that I can adjust the camera's rendering range using znear and zfar.

I have a few questions:

These parameters(znear , zfar) seem to be global. How can I set different rendering ranges for different cameras?
What can the frustum parameter be used for? I thought only objects within the frustum range could be rendered. I tried changing the size of the frustum, but the camera's rendered image doesn't seem to change. Objects outside the frustum are still visible in the camera. The rendering range seems to only be related to znear and zfar.

Here is my test model:

minimal XML

<mujoco>
  <statistic extent="1"/>
  <visual>
    <map znear="0.01" zfar="10"/>
    <rgba frustum="1. 1. 0 0.2"/>
    <scale frustum="1"/>
  </visual>

  <asset>
    <texture name="grid" type="2d" builtin="checker" width="512" height="512" rgb1=".8 .6 .4" rgb2=".2 .3 .4"/>
    <material name="grid" texture="grid" texrepeat="9 16" texuniform="false" reflectance=".2"/>
  </asset>

  <worldbody>
    <light pos="0 0 3"/>
    <geom type="plane" size="10 10 .01"/>
    <camera pos="0 2 1" xyaxes="0 -1 0 0 0 1" focal="8e-3 8e-3" resolution="1920 1200"
        sensorsize="9.6e-3 6e-3" principalpixel="200 0"/>
    <body pos="0 0 0">
        <joint type="slide" axis="1 0 0" limited="true" range="-1 20"/>
        <geom name="box2" type="box" size=".375 .6 .1" pos="1 2 1" material="grid" euler="0 90 0"/>
    </body>
  </worldbody>
</mujoco>

the viewpoint of camera0.

aftersomemath · 2024-03-21T15:28:09Z

aftersomemath
Mar 21, 2024

Hi,

My understanding is that the frustum element of visual/scale is just for rendering a visualization of the camera's frustum. It does not actually effect the rendering process.

In theory you should be able to set MjvScene.mjvGLCamera.frustum_* as you see fit in order to set znear and zfar per camera.

These variables are normally computed from the global znear and zfar options during the call to mjv_updateCamera which itself is called from mjv_updateScene. Normally you would call mjv_updateScene before rendering a frame, however I think you should be able to recalculate mjvGLCamera.frustum_* between the calling mjv_updateScene and the subsequent call to mjr_render. I have not tried this myself though.

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LinShuang22 · 2024-03-29T03:37:09Z

LinShuang22
Mar 29, 2024
Author

@aftersomemath Thank you, I also noticed the 'glcamera' low-level camera. But I don't know how to use it. Mujoco's description of it is a bit sparse. Could you provide an example program? : )

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