Feature request: Add true color support for vegetation in simulated point clouds

[realjoshqsun]

Is your feature request related to a problem? Please describe.
I'm currently using HELIOS++ to simulate ULS and ALS point clouds with detailed voxel representations for vegetation modeling. While the simulation accurately captures the geometric structure of trees, I'm unable to visualize the true colors of the trees in the resulting point clouds.

Describe the solution you'd like
I would like HELIOS++ to support color attribute preservation in the simulated point clouds. Specifically, when using the "detailedVoxels" filter with material files (as seen in the configuration where matfile and matname parameters are specified), the color information from these materials should be transferred to the resulting point cloud. This would enable more realistic visualizations where the simulated trees maintain their natural coloration in the output data.

Describe alternatives you've considered
I've considered post-processing the point clouds to add color information based on classification or height values, but this doesn't provide the true color representation that would be available from the material definitions already present in the scene configuration. I've also looked into using other simulation software, but HELIOS++ provides the best voxel-based vegetation modeling capabilities for my needs.

Related issues
I haven't found any existing issues specifically addressing color preservation in point clouds generated from material-defined voxels.