Nvidia Corporation

Gregory Muthler

John Matthew Burgess

William P Newhall, Jr

Ronald Charles Babich, Jr

Magnus Andersson

Samuli Matias Laine

Tero Tapani Karras

Ignacio Llamas

Timo Oskari Aila

James Robertson

Craig E Kolb

Henry Packard Moreton

Yury Y Uralsky

Ian Kwong

Nikhil Dixit

Edward Biddulph

Jack H Choquette

Marco Salvi

Peter B Holmqvist

George R Lynch

Karan Mehra

Christoph Kubisch

Ian Chi Yan Kwong

Jerome Francis Duluk, Jr

Steven E Molnar

Emmett Michael Kilgariff

James Michael O'Connor

Patrick Richard Brown

Wishwesh Anil Gandhi

David Kirk McAllister

Timothy John Purcell

Christian Amsinck

Eric Enderton

Nick Barrow-Williams

Hemayet Hossain

Timo Tapani Viitanen

Levi Oliver

Johannes Deligiannis

Magnus Anderson

Josh Noel

Techniques applicable to a ray tracing hardware accelerator for traversing a hierarchical acceleration structure with reduced round-trip communications with a processor are disclosed. The reduction of round-trip communications with a processor during traversal is achieved by having a visibility mask that defines visibility states for regions within a geometric primitive available to be accessed in the ray tracing hardware accelerator when a ray intersection is detected for the geometric primitive.

Accelerating triangle visibility tests for real-time ray tracing

To improve the efficiency of bounding volumes in a hardware based ray tracer, we employ a sheared axis-aligned bounding box to approximate an oriented bounding box typically defined by rotations. To achieve this, the bounding volume hierarchy builder shears an axis-aligned box to fit tightly around its enclosed oriented geometry in top level or bottom level space, then computes the inverse shear transform. The bounds are still stored as axis-aligned boxes in memory, now defined in the new sheared coordinate system, along with the derived parameters to transform a ray into the sheared coordinate system before testing intersection with the boxes. The ray-bounding volume intersection test is performed as usual, just in the new sheared coordinate system. Additional efficiencies are gained by constraining the number of shear dimensions, constraining the shear transform coefficients to a quantized list, sharing a shear transform across a collection of bounds, performing a shear transform only for ray-bounds testing and not for ray-geometry intersection testing, and adding a specialized shear transform calculator/accelerator to the hardware.

Efficiency of ray-box tests

Enhanced techniques applicable to a ray tracing hardware accelerator for traversing a hierarchical acceleration structure and its underlying primitives are disclosed. For example, traversal speed is improved by grouping processing of primitives sharing at least one figure (e.g., a vertex or an edge) during ray-primitive intersection testing. Grouping the primitives for ray intersection testing can reduce processing (e.g., projections and transformations of primitive vertices and/or determining edge function values) because at least a portion of the processing results related to the shared feature in one primitive can be used to determine whether the ray intersects another primitive(s). Processing triangles sharing an edge can double the culling rate of the triangles in the ray/triangle intersection test without replicating the hardware.

Hardware acceleration for ray tracing primitives that share vertices

A Displaced Micro-mesh (DMM) primitive enables high complexity geometry for ray and path tracing while minimizing the associated builder costs and preserving high efficiency. A structured, hierarchical representation implicitly encodes vertex positions of a triangle micro-mesh based on a barycentric grid, and enables microvertex displacements to be encoded efficiently (e.g., as scalars linearly interpolated between minimum and maximum triangle surfaces). The resulting displaced micro-mesh primitive provides a highly compressed representation of a potentially vast number of displaced microtriangles that can be stored in a small amount of space. Improvements in ray tracing hardware permit automatic processing of such primitive for ray-geometry intersection testing by ray tracing circuits without requiring intermediate reporting to a shader.

Displaced micro-meshes for ray and path tracing

Techniques are disclosed for improving the throughput of ray intersection or visibility queries performed by a ray tracing hardware accelerator. Throughput is improved, for example, by releasing allocated resources before ray visibility query results are reported by the hardware accelerator. The allocated resources are released when the ray visibility query results can be stored in a compressed format outside of the allocated resources. When reporting the ray visibility query results, the results are reconstructed based on the results stored in the compressed format. The compressed format storage can be used for ray visibility queries that return no intersections or terminate on any hit ray visibility query. One or more individual components of allocated resources can also be independently deallocated based on the type of data to be returned and/or results of the ray visibility query.

Early release of resources in ray tracing hardware

Methods and systems are described in some examples for changing the traversal of an acceleration data structure in a highly dynamic query-specific manner, with each query specifying test parameters, a test opcode and a mapping of test results to actions. In an example ray tracing implementation, traversal of a bounding volume hierarchy by a ray is performed with the default behavior of the traversal being changed in accordance with results of a test performed using the test opcode and test parameters specified in the ray data structure and another test parameter specified in a node of the bounding volume hierarchy. In an example implementation a traversal coprocessor is configured to perform the traversal of the bounding volume hierarchy.

Query-specific behavioral modification of tree traversal

Techniques applicable to a ray tracing hardware accelerator for traversing a hierarchical acceleration structure with reduced false positive ray intersections are disclosed. The reduction of false positives may be based upon one or more of selectively performing a secondary higher precision intersection test for a bounding volume, identifying and culling bounding volumes that degenerate to a point, and parametrically clipping rays that exceed certain configured distance thresholds.

Reducing false positive ray traversal in a bounding volume hierarchy

Reducing false positive ray traversal using point degenerate culling

Enhanced techniques applicable to a ray tracing hardware accelerator for traversing a hierarchical acceleration structure are disclosed. For example, traversal efficiency is improved by combining programmable traversals based on ray operations with per-node static configurations that modify traversal behavior. The per-node static configurations enable creators of acceleration data structures to optimize for potential traversals without necessarily requiring detailed information about ray characteristics and ray operations used when traversing the acceleration structure. Moreover, by providing for selective exclusion of certain nodes using per-node static configurations, less memory is needed to express an acceleration structure that includes, for example, different geometric levels of details corresponding to a single object.

Enhanced techniques for traversing ray tracing acceleration structures

Ray tracing hardware accelerators supporting motion blur and moving/deforming geometry are disclosed. For example, dynamic objects in an acceleration data structure are encoded with temporal and spatial information. The hardware includes circuitry that test ray intersections against moving/deforming geometry by applying such temporal and spatial information. Such circuitry accelerates the visibility sampling of moving geometry, including rigid body motion and object deformation, and its associated moving bounding volumes to a performance similar to that of the visibility sampling of static geometry.

Ray tracing hardware acceleration for supporting motion blur and moving/deforming geometry

An alternate root tree or graph structure for ray and path tracing enables dynamic instancing build time decisions to split any number of geometry acceleration structures in a manner that is developer transparent, nearly memory storage neutral, and traversal efficient. The resulting traversals only need to partially traverse the acceleration structure, which improves efficiency. One example use reduces the number of false positive instance acceleration structure to geometry acceleration structure transitions for many spatially separated instances of the same geometry.

Generation and traversal of partial acceleration structures for ray tracing

In a ray tracer, a cache for streaming workloads groups ray requests for coherent successive bounding volume hierarchy traversal operations by sending common data down an attached data path to all ray requests in the group at the same time or about the same time. Grouping the requests provides good performance with a smaller number of cache lines.

Method for efficient grouping of cache requests for datapath scheduling

Reducing false positive ray traversal using ray clipping

A bounding volume is used to approximate the space an object occupies. If a more precise understanding beyond an approximation is required, the object itself is then inspected to determine what space it occupies. Often, a simple volume (such as an axis-aligned box) is used as bounding volume to approximate the space occupied by an object. But objects can be arbitrary, complicated shapes. So a simple volume often does not fit the object very well. That causes a lot of space that is not occupied by the object to be included in the approximation of the space being occupied by the object. Hardware-based techniques are disclosed herein, for example, for efficiently using multiple bounding volumes (such as axis-aligned bounding boxes) to represent, in effect, an arbitrarily shaped bounding volume to better fit the object, and for using such arbitrary bounding volumes to improve performance in applications such as ray tracing.

Hardware-based techniques applicable for ray tracing for efficiently representing and processing an arbitrary bounding volume

Growing community of inventors

Austin, TX, United States of America

Gregory Muthler