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Lysa
0.0
Lysa 3D Engine
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Lysa
0.0
Lysa 3D Engine
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RotatingAssetScene.cpp : onProcess The rotation is implemented entirely in RotatingAssetScene::onProcess. The method is called once per rendered frame by the PROCESS event, which passes the elapsed time since the previous frame as alpha (in seconds).
rotationAngle is incremented by alpha * ROTATION_SPEED on each call. Because alpha is the actual elapsed time, the angular velocity is constant regardless of frame rate.
ROTATION_SPEED is 0.025f rad/s, giving a slow, deliberate rotation well-suited for inspecting a static asset.
Once rotationAngle exceeds 2π, the full circle is subtracted. Without this wrap, a float accumulating indefinitely would gradually lose sub-radian precision after several hours of runtime.
Lysa exposes a concise math library based on hlslpp. The types and free functions most commonly used for scene transforms:
| Symbol | Description |
|---|---|
lysa::float4x4 | Row-major 4×4 matrix |
float4x4::identity() | Returns the identity matrix |
float4x4::rotation_x/y/z(radians) | Single-axis rotation matrix |
float4x4::translation(x, y, z) | Translation matrix |
float4x4::scale(s) | Uniform scale matrix |
lysa::mul(A, B) | Matrix multiplication (A applied first, then B) |
lysa::radians(degrees) | Degrees-to-radians conversion |
lysa::perspective(fov, aspect, near, far) | Reversed-Z perspective projection |
lysa::float3, lysa::float2, lysa::float4 | Vector types with arithmetic operators |
lysa::quaternion | Quaternion type (useful for interpolated rotations) |
lysa::euler_angles(q) | Extracts Euler angles from a quaternion |
Matrix multiplication order follows row-vector convention: in mul(localTransform, parentTransform), the local transform is applied first in object space, and then the result is transformed into the parent's space. This matches the SceneInstance::update() implementation.
lysa::float4x4::rotation_y(rotationAngle) constructs a rotation matrix around the world Y-axis and assigns it as root's local transform. Because the loaded asset is a child of root, the rotation propagates to the entire imported hierarchy through the recursive root.update() call.
SceneTree::onProcess(alpha) is called last. It calls root.update() to recompute all global transforms in the tree, then updateInstance(root) to push the new transforms to the renderer (see Scene tree).
onProcess override always calls the base class last, after all mutations. Calling SceneTree::onProcess first and then mutating root would push stale transforms to the renderer for that frame.Next : Application class
2.1.0