Intersection Testing in a Ray Tracing System Using Scaled Ray Components

An intersection testing module, for use in a ray tracing system, configured to determine whether a ray intersects a three-dimensional axis-aligned volume, wherein the volume is defined by a front-facing plane and a back-facing plane for each dimension of the three-dimensional axis-aligned volume, the intersection testing module being configured to:

• selectively reverse axes for the components of the ray and the axis-aligned volume to provide that Du≥0, Dv≥0 and Dw>0, wherein Du, Dv and Dw are components of a ray direction vector, D, for the ray, and wherein Dw is the major component of the ray direction vector;
• determine scaled inverse ray components ρu and ρv, wherein
• ρ
• u
• =
• AD
• w
• D
• u
• ⁢
• and
• ⁢
• ρ
• v
• =
• AD
• w
• D
• v
• ,
• and wherein A is a scalar value;
• determine a scaled minimum culling distance, tmin,scaled, using a result of multiplying an unscaled minimum culling distance for the ray, tmin,unscaled, by the magnitude of ADw;
• determine a scaled maximum culling distance, tmax,scaled, using a result of multiplying an unscaled maximum culling distance for the ray, tmax,unscaled, by the magnitude of ADw;
• determine scaled intersection distances to the planes defining the volume using the scaled inverse ray components;
• identify the largest of the determined scaled intersection distances to a front-facing plane of the volume;
• identify the smallest of the determined scaled intersection distances to a back-facing plane of the volume;
• determine whether:
• (i) the identified largest scaled intersection distance to a front-facing plane of the volume is no greater than the identified smallest scaled intersection distance to a back-facing plane of the box;
• (ii) the identified largest scaled intersection distance to a front-facing plane of the volume is no greater than the scaled maximum culling distance, tmax,scaled;
• and
• (iii) the identified smallest scaled intersection distance to a back-facing plane of the volume is no less than the scaled minimum culling distance, tmin,scaled;
• and
• determine that the ray intersects the volume if all of the three determinations (i) to (iii) are satisfied, and determine that the ray misses the volume if one or more of the three determinations (i) to (iii) are not satisfied.

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 which is configured for use in a ray tracing system, the intersection testing module being configured to determine whether a ray intersects a three-dimensional axis-aligned volume, wherein the volume is defined by a front-facing plane and a back-facing plane for each dimension of the three-dimensional axis-aligned volume, the intersection testing module being configured to:

• selectively reverse axes for the components of the ray and the axis-aligned volume to provide that Du≥0, Dv≥0 and Dw>0, wherein Du, Dv and Dw are components of a ray direction vector, D, for the ray, and wherein Dw is the major component of the ray direction vector;
• determine scaled inverse ray components ρu and ρv, wherein
• ρ
• u
• =
• AD
• w
• D
• u
• ⁢
• and
• ⁢
• ρ
• v
• =
• AD
• w
• D
• v
• ,
• and wherein A is a scalar value;
• determine a scaled minimum culling distance, tmin,scaled, using a result of multiplying an unscaled minimum culling distance for the ray, tmin,unscaled, by the magnitude of ADw;
• determine a scaled maximum culling distance, tmax,scaled, using a result of multiplying an unscaled maximum culling distance for the ray, tmax,unscaled, by the magnitude of ADw;
• determine scaled intersection distances to the planes defining the volume using the scaled inverse ray components;
• identify the largest of the determined scaled intersection distances to a front-facing plane of the volume;
• identify the smallest of the determined scaled intersection distances to a back-facing plane of the volume;
• determine whether:
• (i) the identified largest scaled intersection distance to a front-facing plane of the volume is no greater than the identified smallest scaled intersection distance to a back-facing plane of the volume;
• (ii) the identified largest scaled intersection distance to a front-facing plane of the volume is no greater than the scaled maximum culling distance, tmax,scaled;
• and
• (iii) the identified smallest scaled intersection distance to a back-facing plane of the volume is no less than the scaled minimum culling distance, tmin,scaled;
• and
• determine that the ray intersects the volume if all of the three determinations (i) to (iii) are satisfied, and determine that the ray misses the volume if one or more of the three determinations (i) to (iii) are not satisfied.