screen_to_ray()

Ray MayaFlux::Kinesis::screen_to_ray ( double  window_x, double  window_y, uint32_t  width, uint32_t  height, const ViewTransform &  vt  )

inline

Construct a world-space ray from window pixel coordinates.

Parameters

window_x	X in window space [0, width]
window_y	Y in window space [0, height] (top-left origin)
width	Window width in pixels.
height	Window height in pixels.
vt	Active ViewTransform (view + projection matrices).

Returns

Ray with origin at the near plane and normalized direction into the scene.

Unprojects two points at z=0 (near) and z=1 (far) in NDC through the inverse of projection * view. The resulting world-space positions define the ray origin and direction.

Definition at line 53 of file HitTest.hpp.

{
    float ndc_x = (static_cast<float>(window_x) / static_cast<float>(width)) * 2.0F - 1.0F;
    float ndc_y = 1.0F - (static_cast<float>(window_y) / static_cast<float>(height)) * 2.0F;
 
    glm::mat4 inv_vp = glm::inverse(vt.projection * vt.view);
 
    glm::vec4 near_h = inv_vp * glm::vec4(ndc_x, ndc_y, 0.0F, 1.0F);
    glm::vec4 far_h = inv_vp * glm::vec4(ndc_x, ndc_y, 1.0F, 1.0F);
 
    glm::vec3 near_w = glm::vec3(near_h) / near_h.w;
    glm::vec3 far_w = glm::vec3(far_h) / far_h.w;
 
    return { .origin = near_w, .direction = glm::normalize(far_w - near_w) };
}

References MayaFlux::Kinesis::ViewTransform::projection, MayaFlux::Kinesis::ViewTransform::view, and width.