US 12,469,206 B2
Intersection testing in a ray tracing system using scaled ray components
Rostam King, Hertfordshire (GB)
Assigned to Imagination Technologies Limited, Kings Langley (GB)
Filed by Imagination Technologies Limited, Kings Langley (GB)
Filed on Mar. 15, 2023, as Appl. No. 18/122,105.
Application 18/122,105 is a continuation of application No. 17/701,606, filed on Mar. 22, 2022, granted, now 11,610,361, issued on Mar. 21, 2023.
Claims priority of application No. 2104056 (GB), filed on Mar. 23, 2021.
Prior Publication US 2023/0215077 A1, Jul. 6, 2023
This patent is subject to a terminal disclaimer.
Int. Cl. G06T 15/06 (2011.01); G06T 15/00 (2011.01)
CPC G06T 15/06 (2013.01) [G06T 15/005 (2013.01); G06T 2210/12 (2013.01); G06T 2210/21 (2013.01)] 20 Claims
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1. A method of determining, in a ray tracing system, 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 of the dimensions, u, ν and w, of the three-dimensional axis-aligned volume, wherein bmin,u is a constant u component value of the front-facing plane for the u dimension, bmax,u is a constant u component value of the back-facing plane for the u dimension, bmin,ν is a constant ν component value of the front-facing plane for the ν dimension, bmax,ν is a constant ν component value of the back-facing plane for the ν dimension, bmin,w is a constant w component value of the front-facing plane for the w dimension, and bmax,w is a constant w component value of the back-facing plane for the w dimension, the method comprising:
selectively reversing axes for components of the ray and the axis-aligned volume to provide that Du≥0, Dν≥0 and Dw>0, wherein Du, Dν and Dw are components of a ray direction vector, D, for the ray, wherein Dw is the major component of the ray direction vector;
determining scaled ray components ρu and ρν, wherein

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determining 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 Dw;
determining 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 Dw;
determining cross-multiplication values of Aρubmin,ν, Aρubmin,u, Aρubmax,u and Aρνbmax,u, wherein A is a scalar value;
determining a cross-multiplication value of one or both of: (i) Aρubmin,w and (ii) Aρνbmin,w;
determining a cross-multiplication value of one or both of: (i) Aρubmax,w and (ii) Aρνbmax,w;
using the determined cross-multiplication values to:
identify which of the front-facing planes intersects the ray furthest along the ray; and
identify which of the back-facing planes intersects the ray least far along the ray;
determining whether the ray intersects the identified front-facing plane of the volume at a position that is no further along the ray than the position at which the ray intersects the identified back-facing plane;
determining whether ρ−tmax,scaled is no less than b−, wherein ρ−=ρu and b−=bmin,u if the front-facing plane for the u dimension is the identified front-facing plane, wherein ρ−=ρν and b−=bmin,ν if the front-facing plane for the ν dimension is the identified front-facing plane, and wherein ρ−=1 and b−=bmin,w if the front-facing plane for the w dimension is the identified front-facing plane;
determining whether ρ+tmin,scaled is no greater than b+, wherein ρ+=ρu and b+=bmax,u if the back-facing plane for the u dimension is the identified back-facing plane, wherein ρ+=ρν and b+=bmax,ν if the back-facing plane for the ν dimension is the identified back-facing plane, and wherein ρ+=1 and b+=bmax,w if the back-facing plane for the w dimension is the identified back-facing plane; and
determining that the ray intersects the volume if all three of: (i) it is determined that the ray intersects the identified front-facing plane of the volume at a position that is no further along the ray than the position at which the ray intersects the identified back-facing plane, (ii) it is determined that ρ−tmax,scaled is no less than b−, and (iii) it is determined that ρ+tmin,scaled is no greater than b+, otherwise determining that the ray misses the volume.