A minimalist and platform-agnostic interactive/real-time raytracer.
Strong emphasis on simplicity, ease of use and almost no setup to get started with.

Written in plain C and can be complied in either C or C++.

This project extends SlimEngine.

Optional GPU support is provided via CUDA.
The same C code is cross-compiled (no CUDA libraries used).
Compiling using CUDA allows for dynamic toggling between rendering on the CPU or the GPU.

Architecture:

The platform layer only uses operating-system headers (no standard library used).
The application layer itself (non-CUDA) has no dependencies, apart from the standard math header.
It is just a library that the platform layer uses - it has no knowledge of the platform.

More details on this architecture here.

Features:

All features of SlimEngine are available here as well.
Additional features include raytracing facilities:

• Acceleration Structure (BVH) construction and traversal
• Intersection shaders for triangular meshes and implicit geometry
• Debug render modes (Depth, Normal, UV and BVH-preview)
• Physically based materials (Micro-facet Cook-Torrance BRDF)
• Raytracing specific shaders (Glass, Mirror, Area lights)
• Textures (Bi-Linear filtered) with adaptive mip-selection (using ray cones)
  

The following example apps demonstrate how to use SlimTracin's features:
Note: Each example comes with CMake targets for CPU-only (no CUDA required) or GPU-enabled (requiring CUDA)

• Implicit Geometry: Quad, Box, Sphere and Tetrahedra, all with UV-based transparency
  
  
• Point lights: Can be moved around and scaled (changing their light intensity)
  
  
• Area Lights: Emissive quads can be used as rectangular area lights
  
  

  

• Classic Materials: Lambert, Blinn, Phong
  
  

  

• PBR Materials: Cook-Torrance BRDF (Schlick/Smith GGX)
  
  
• Reflective/Refractive Materials: For glasses and mirrors (bounce count is controlled globally)
  
  

  

• Meshes: Transformable and can have smooth shading using vertex normal interpolation
  
  

  

  Mesh files are in a format native to the renderer which is optimized for ray/triangle intersection.
  
• Textures: Albedo, Normal
  
  
  Textures can be loaded from files for use as albedo or normal maps.
  Texture files are in a format native to the renderer and optimized for filtered sampling.
  
• Render Modes: Beauty, Depth, Normals, UVs and BVHs
  
  

  

  BVHs can be shown as a wireframe overlay in any render mode.
  
  The BVH of the scene updates dynamically as primitives are transformed.
  The BVH of meshes are only built once when a mesh file is first created.
  Mesh primitives can be transformed dynamically because tracing is done in the local space of each primitive.
  

Converting .bmp files to the native .texture files can be done with a provided CLI tool:
./bmp2texture src.bmp trg.texture [-m] [-w]
-m : Generate mip-maps
-w : Wrap-around

Converting .obj files to the native .mesh files can be done with a provided CLI tool:
./obj2mesh src.obj trg.mesh [-i]
-i : Invert triangle winding order (CW to CCW)
Note: SlimTracin's .mesh files are not the same as SlimEngine's ones.

SlimTracin does not come with any GUI functionality at this point.
Some example apps have an optional HUD (heads up display) that shows additional information.
It can be toggled on or off using thetab key.

All examples are interactive using SlimTracing's facilities having 2 interaction modes:

1. FPS navigation (WASD + mouse look + zooming)
   
2. DCC application (default)
   

Double clicking the left mouse button anywhere within the window toggles between these 2 modes.

Entering FPS mode captures the mouse movement for the window and hides the cursor.
Navigation is then as in a typical first-person game (plus lateral movement and zooming):

Move the mouse to freely look around (even if the cursor would leave the window border)
Scroll the mouse wheel to zoom in and out (changes the field of view of the perspective)
Hold W to move forward
Hold S to move backward
Hold A to move left
Hold D to move right
Hold R to move up
Hold F to move down

Exit this mode by double clicking the left mouse button.

The default interaction mode is similar to a typical DCC application (i.e: Maya):
The mouse is not captured to the window and the cursor is visible.
Holding the right mouse button and dragging the mouse orbits the camera around a target.
Holding the middle mouse button and dragging the mouse pans the camera (left, right, up and down).
Scrolling the mouse wheel dollys the camera forward and backward.

Clicking the left mouse button selects an object in the scene that is under the cursor.
Holding the left mouse button while hovering an object and then dragging the mouse,
moves the object parallel to the screen.

Holding alt highlights the currently selecte object by drawing a bounding box around it.
While alt is still held, if the cursor hovers the selected object's bounding box,
mouse interaction transforms the object along the plane of the bounding box that the cursor hovers on:
Holding the left mouse button and dragging the mouse moves the object.
Holding the right mouse button and dragging the mouse rotates the object.
Holding the middle mouse button and dragging the mouse scales the object.
(mouse wheel interaction is disabled while alt is held)

In some examples, further interaction is enabled while holding ctrl or shift
using the mouse wheel as a virtual "slider":
Holding shift and scrolling the mouse wheel cycles the assigned material for the selected object.
Holding ctrl and scrolling the mouse wheel increases or decreases the trace-height*
(how many times rays are allowed to bounce around between reflective or refractive objects)