Add Screen-Space Ambient Occlusion and infinite ground plane support

[Copilot]

Implements SSAO using screen-space derivatives for single-pass occlusion and adds support for invisible ground planes that display only AO shadows.

Changes

Shader (shaders/phong_with_wireframe_ssao.frag)

• Single-pass SSAO using dFdx/dFdy derivatives
• Circular sampling pattern (configurable 1-16 samples)
• AO applied only to ambient term, preserving direct lighting
• GLSL 1.40 compatible (float uniforms, no defaults)

Python API (python/OffscreenRenderer.py)

• Mesh: conditional SSAO shader loading via use_ssao parameter
• MeshRenderer.enableSSAO(enabled, radius, bias, samples): global SSAO control
• MeshRenderer.addInfiniteGroundPlane(z, size, color, only_show_ao): creates large planes displaying AO only
• Float/boolean conversions for shader uniform compatibility

Build (src/python_bindings/CMakeLists.txt)

• pybind11 v2.6.1 → v2.11.1 for Python 3.12 compatibility

Example (python/MeshDemo.ipynb)

• SSAO demonstration with parameter tuning
• Invisible ground plane demonstration

Usage

renderer = ogl.MeshRenderer(800, 600)
renderer.setMesh(vertices, faces, normals, colors)

# Enable SSAO
renderer.enableSSAO(enabled=True, radius=0.5, bias=0.025, samples=16)

# Add invisible ground plane showing only AO shadows
renderer.addInfiniteGroundPlane(z=0.0, size=1000.0, only_show_ao=True)

renderer.render()
renderer.save('output.png')

Limitations

• Derivative-based approach provides approximation, not true geometric occlusion
• No bilateral blur pass (may appear noisy)
• Maximum 16 samples per fragment

Warning

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Original prompt

Implement Screen-Space Ambient Occlusion in this codebase. Add an option to add an infinite invisible ground plane at z=0 that will only display ambient occlusion. Add an example how to enable ssao in MeshDemo.ipynb

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