Add various shape type

[pjessesco]

• Fix TriangleMesh to handle triangle vertex by index (no longer store duplicated vertices)
• Add Instance shape type for multiple instances of the same shape with different transforms :

{
    "type" : "instance",
    "shapes": [
        {
            "type" : "obj",
            "path" : "cube.obj",
            "bsdf" : {
                "type" : "conductor",
                "material" : "Ag",
                "ex_ior" : 1.0
            },
            "to_world" : [
                {
                    "type" : "rotate_y",
                    "degree" : 30
                }
            ]
        },
        // ... other shapes
    ],
    "instances": [
        {
            "to_world": [1.0, 0.0, 0.0, -2.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 5.0, 0.0, 0.0, 0.0, 1.0]
        },
        {
            "to_world": [1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 5.0, 0.0, 0.0, 0.0, 1.0]
        },
        {
            "to_world": [1.0, 0.0, 0.0, 2.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 5.0, 0.0, 0.0, 0.0, 1.0]
        }
    ]
}

• Add InlineTriangleMesh to specify triangle mesh in json file :

{
    "type": "trianglemesh",
    "P": [-0.5, -0.5, 0,  0.5, -0.5, 0,  0.5, 0.5, 0,  -0.5, 0.5, 0],
    "indices": [0, 2, 1,  0, 3, 2],
    "to_world": [
        1.0, 0.0, 0.0, 0.0,
        0.0, 0.707106, -0.707106, -1.5,
        0.0, 0.707106, 0.707106, 0.0,
        0.0, 0.0, 0.0, 1.0
    ],
    "bsdf": {
        "type": "diffuse",
        "albedo": [0.8, 0.2, 0.2]
    }
},

[Copilot]

Pull request overview

This PR extends Caramel’s shape system by introducing instancing and an inline triangle-mesh JSON format, while also refactoring mesh shapes (OBJ/PLY/inline) to share a unified TriangleMesh implementation based on indexed triangles.

Changes:

• Refactors OBJ/PLY meshes onto a shared TriangleMesh base with m_face_indices and a common finalize() path (AABB/area/BVH/solid-angle polygon extraction).
• Adds Instance shape type (per-placement transform around a shared template shape).
• Adds InlineTriangleMesh and scene parsing support for "type": "trianglemesh" with inline vertex/index arrays; adds/updates tests and a new render test scene.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
test/unit_tests.cpp	Adds unit tests for Instance ray intersection and inline triangle mesh behavior.
test/simple_render_test.cpp	Adds a new render regression test (test7) and scaffolding for instance-related render tests (currently commented).
src/shapes/triangle_mesh.cpp	Introduces shared TriangleMesh implementation (finalize, sampling, BVH integration, solid-angle polygon extraction).
src/shapes/plymesh.cpp	Simplifies PLY mesh loading to populate shared TriangleMesh buffers and call finalize().
src/shapes/objmesh.cpp	Updates OBJ loading to weld vertices by (v/n/uv) and emit indexed faces into TriangleMesh.
src/shapes/instance.cpp	Implements instanced shape intersection + transformed AABB, sampling, and solid-angle PDF.
src/shapes/inline_triangle_mesh.cpp	Implements mesh construction directly from inline vertex/index arrays and calls finalize().
src/scene_parser.cpp	Adds parsing for "type":"instance" expansion and for inline "type":"trianglemesh".
include/shape.h	Refactors TriangleMesh to a concrete base class; adds InlineTriangleMesh + Instance declarations.
include/scene_parser.h	Declares parse_instanced_shapes() and documents instance schema.
CMakeLists.txt	Registers new shape sources in the build.

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[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 3 comments.