Simpler debug renderer interface?

[eliasdaler]

Hello.

I'm currently a bit struggling to implement my own debug renderer because it's quite complex. I understand that this is needed to implement an efficient renderer, but what if there was a simpler wireframe renderer which could be implemented in more of an "immediate mode" style?

For example, implementing debug renderer for Bullet was much easier (see docs here) - you only need to implement three methods: drawLine, drawContactPoint, reportErrorWarning and draw3dText.

To get basic wireframe rendering working, you only need to implement drawLine(from, to, color) - and this is already enough to at least see the outlines/wireframes of the bodies in your physics scene - which can be enough for a start.

What do you think? I think that this might be a pretty handy feature for people who want to quickly jump in, add some bodies into the scene and see that they're at correct positions, orientations etc.

[SSNTails]

The immediate mode debug renderer in Bullet would instantly kill my fps, but it was decent enough to be able to create smaller worlds with test cases and resolve issues.

[eliasdaler]

I managed to get much better performance by doing simple frustum culling of lines which weren't visible to the camera. Can probably reduce z-far a lot to not draw lines too far away.

[MrOnlineCoder]

I personally also did not succeed in writing it from the first try, due to need of figuring out how to correctly re-implement Batch interface. However, after I've done it, I have not yet come back to modify it - it works fine so far so it's mostly 'write once and forget' approach.

You can also just stub some methods and do nothing in them, as I did for example with DrawText3D because I didn't have text rendering at that time, and needed mostly just visual drawings of the bodies and their shapes, rather than textual info.

IMHO, changing current debug renderer interface would be a quite breaking change, so it's either better to add an additional "simplified" renderer so you can switch between them when needed, or just have ready-to-use implementations of renderers for different backends and libraries like SDL/OpenGL/Vulkan that you can copy-paste into your project with minimal changes.

[eliasdaler]

I don't think the current interface needs to be simplified - maybe Jolt can provide a "stub" implementation which hides details of batching, LOD etc. and only requires you to implement "draw line" function - that would certainly be of huge help.

For example, this implementation could store batches internally and call "DrawLine" for each triangle each frame for each triangle side.

[jrouwe]

I just added DebugRendererSimple

[cuppajoeman]

Hello.

I'm currently a bit struggling to implement my own debug renderer because it's quite complex. I understand that this is needed to implement an efficient renderer, but what if there was a simpler wireframe renderer which could be implemented in more of an "immediate mode" style?

For example, implementing debug renderer for Bullet was much easier (see docs here) - you only need to implement three methods: drawLine, drawContactPoint, reportErrorWarning and draw3dText.

To get basic wireframe rendering working, you only need to implement drawLine(from, to, color) - and this is already enough to at least see the outlines/wireframes of the bodies in your physics scene - which can be enough for a start.

What do you think? I think that this might be a pretty handy feature for people who want to quickly jump in, add some bodies into the scene and see that they're at correct positions, orientations etc.

I implemented the debug renderer in opengl a few weeks ago, It's a basic wireframe renderer using glDrawElements to draw a batch of triangles at once, so it's better than the single line approach: https://github.com/opengl-toolbox/mwe_physics_world_with_character/blob/main/graphics/physics_debug_renderer/physics_debug_renderer.hpp feel free to use it as reference