RMIP: fast tessellation-free GPU displacement ray tracing via inversion and oblong bounding simulation
A system generates, based on a displacement bounds data structure and a triangle mesh modeling a surface of a 3D virtual object within a 3D virtual scene, a displaced triangle mesh including one or more displaced surface bounding prisms, each of the one or more displaced surface bounding prisms displaced from a respective base triangle of a plurality of base triangles of the triangle mesh structure based on displacement bounds defined in a displacement bounds data structure for an area of a 2D texture space corresponding to a location of the respective base triangle defined by the 3D virtual scene. The system performs, using the displaced triangle mesh structure, a ray tracing process for a ray associated with a pixel of a 2D image of the virtual scene including determining, responsive to determining the ray intersects the particular displaced surface bounding prism, a location of an intersection of the ray.
1 . A method performed by one or more computing devices associated with a scene rendering system, comprising:
generating, based on a triangle mesh structure that models a surface of a three-dimensional (3D) virtual object within 3D virtual scene, a displaced triangle mesh structure comprising one or more displaced surface bounding prisms, each of the one or more displaced surface bounding prisms displaced from a respective base triangle of a plurality of base triangles of the triangle mesh structure based on displacement bounds defined in a displacement bounds data structure for an area of a two-dimensional (2D) texture space corresponding to a location of the respective base triangle defined by the 3D virtual scene; and
performing, using the displaced triangle mesh structure, a ray tracing process for a ray associated with a pixel of a 2D image of the virtual scene, wherein performing the ray tracing process comprises:
responsive to determining that the ray intersects a particular displaced surface bounding prism of the one or more displaced surface bounding prisms in the 3D virtual scene, determining a location of an intersection of the ray in the 2D texture space.
2 . The method of claim 1 , further performing the ray tracing process further comprises:
defining a value for the pixel based on the determined location of intersection; and
providing for display, via a user interface, the 2D image of the virtual scene comprising the pixel having the defined value.
3 . The method of claim 1 , wherein the displacement bounds comprise a minimum displacement bound.
4 . The method of claim 1 , wherein the displacement bounds comprise a maximum displacement bound.
5 . The method of claim 1 , wherein the displacement bounds data structure comprises a rectangular minmax image pyramid (RMIP) data structure, wherein the area comprises a rectangular area.
6 . The method of claim 1 , wherein the displacement bounds data structure is generated based on a 2D displacement texture map comprising a plurality of block areas of predetermined size, wherein a size of the area is different from the predetermined size.
7 . The method of claim 1 , further comprising:
accessing a two-dimensional (2D) displacement texture map defining the texture for at least a region of the surface of the 3D virtual object; and
generating, based on the 2D displacement texture map, the displacement bounds data structure that defines displacement bounds for one or more areas in a texture space associated with the 2D displacement texture map, the one or more areas comprising the area.
8 . The method of claim 1 , wherein determining that the ray intersects the particular displaced surface bounding prism in the 3D virtual scene comprises determining a first endpoint and a second endpoint of the ray on the particular displaced surface bounding prism, wherein determining a location of an intersection of the ray at the 2D texture space comprises:
determining, based on the determined first endpoint and the determined second endpoint, an initial bounded area in the 2D texture space;
subdividing, at a middle of the initial bounded area of the 2D texture space, the initial bounded area to generate a first subdivided bounded area and a second subdivided bounded area, wherein a path of the ray intersects the first subdivided bounded area prior to intersecting the second subdivided bounded area;
based on the first subdivided bounded area and the second subdivided bounded area, generating a first subdivided axis-aligned bounding box (“AABB”) corresponding to the first subdivided bounded area and a second subdivided AABB corresponding to the second subdivided bounded area;
determining that the ray intersects the first subdivided AABB at a first AABB endpoint and at a second AABB endpoint;
determining, based on the determined first AABB endpoint and the determined second AABB endpoint, an updated bounded area in the 2D texture space, wherein the updated bounded area has smaller dimensions than the initial bounded area; and
determining, within the updated bounded area of the 2D texture space, the location.