Intersection testing in a ray tracing system using axis-aligned box coordinate components

An intersection testing module, for use in a ray tracing system, configured to transform a ray and a box from a space-coordinate system into a ray-coordinate system, wherein the ray and the box are defined in the space-coordinate system, wherein the ray-coordinate system has an origin at an origin of the ray, the intersection testing module being configured to:

• obtain a ray direction comprising at least components Dx,Dy,Dz, the ray direction vector representing the direction of the ray in the space-coordinate system;
• before performing intersection testing of the ray with the box:
• selectively reverse the components of the ray and the box to ensure that all components of the ray direction vector are non-negative in the space-coordinate system;
• selectively permute the components of the ray and the box to ensure that Dz is the component of the ray direction vector with the greatest magnitude, wherein after the selective permutation and selective reversing Dz≥Dx≥0 and Dz≥Dy≥0;
• and
• translate one or more position vectors defining a position of the box by subtracting the origin of the ray from the one or more position vectors defining the position of the box.

A non-transitory computer readable storage medium having stored thereon an integrated circuit definition dataset that, when processed in an integrated circuit manufacturing system, configures the integrated circuit manufacturing system to manufacture an intersection testing module for use in a ray tracing system, configured to transform a ray and a box from a space-coordinate system into a ray-coordinate system, wherein the ray and the box are defined in the space-coordinate system, wherein the ray-coordinate system has an origin at an origin of the ray, the intersection testing module being configured to:

• obtain a ray direction comprising at least components Dx, Dy, Dz, the ray direction vector representing the direction of the ray in the space-coordinate system;
• before performing intersection testing of the ray with the box:
• selectively reverse the components of the ray and the box to ensure that all components of the ray direction vector are non-negative in the space-coordinate system;
• selectively permute the components of the ray and the box to ensure that Dz is the component of the ray direction vector with the greatest magnitude, wherein after the selective permutation and selective reversing Dz≥Dx≥0 and Dz≥Dy≥0;
• and
• translate one or more position vectors defining a position of the box by subtracting the origin of the ray from the one or more position vectors defining the position of the box.