Repository of the different Computer Graphics projects that I'm working on in my spare time. Mostly focused on shader programming.
The shaders below are implemented in the Unity3D game engine with the Cg shading language. I have tried working with OpenGL, but I do not have anything to showcase. Some of the shaders are based on what I was taught in the Computer Graphics Programing course at AAUtaught by Associate Professor Martin Kraus, which are also partly doccumented at https://en.wikibooks.org/wiki/Cg_Programming/Unity, and the image effect shaders are inspired by Unity 5.x Shaders and Effects Cookbook, which I used as a reference guide.
Table of Contents
This shader is a simple implementation of a basic diffuse shader, which works with multiple light sources, adhering to Lambert’s law. The shader is implemented both as a per-vertex and per-pixel shader.
| Lambertian per-vertex | Lambertian per-pixel |
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In this shader I have implemented the approximate version of the Oren-Nayar diffuse reflectance model for rough surfaces. The approximate version disregards the inter reflectance component of the original model, and instead uses the model described by Equation 30 in Oren and Nayer (1994. When σ is 0 the model should be equal to the Lambertian model. The shader is implemented as a per-pixel shader.
| σ = 0 | σ = 0.3 | σ = 0.6 | σ = 1 |
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In these shaders I have implemented three different shaders based on the Phong reflectance model: Phong, Blinn-Phong and Gouraud. Phong and Blinn-Phong are per-pixel shaders, and Gouraud is the per-vertex variation of the Phong shader.
| Gouraud, α = 5 | Phong, α = 5 | Blinn-Phong, α = 20 |
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This shader uses Schlick’s approximation of the Fresnel term to calculate the specular reflection coefficient used in the light model calculations, which in this case is the aforementioned Phong model. The effect is not that noticeable, but this seems to be the general case for Fresnel contributions, since the effect becomes larger at edges, which may blend in with other scene elements.
| The Fresnel highlights shader. As mentioned, it is quite hard to see the effect |
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In this shader I have implemented a version of the Cook-Torrance specular reflectance / microfacets model, proposed by Cook and Torrance (1982). This model is more complex than the Phong reflectance model, but also provide more accurate results.
The Cook-Torrance model uses three different terms to determine the specular reflectance coefficient, namely a Fresnel term, approximated via Schlick’s equation, a Beckmann distribution term for the distribution of the roughness / microfacets of the material and a Geometric attenuation term to simulate self-occlusion. The shader is implemented as a per-pixel shader, with a Lambertian diffuse element. The shader has a single controllable value, m, for the roughness of the material, which ranges from 0 (smooth) to 1 (rough), with higher values resulting in less highlights.
| m = 0.1 | m = 0.3 | m = 0.6 | m = 1 |
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The Ward anisotropic distribution, proposed by Ward (1992), models the specular coefficient in cases where the material’s reflectance is not isotropic i.e. the specular reflection is not just circular. The model uses two parameters, αx and αy, to control the "brushes" in the x and y directions. If both parameters are equal it reduces to a simple isotropic model. The shader is implemented as a per-pixel shader.
| αx = 0.3, αy = 0.3 | αx = 0.3, αy = 0.6 | αx = 0.6, αy = 0.3 |
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This shader is based on Section 5.1 in Kraus (2005). The shader is a per-pixel shader, and the thickness of the silhouette is controllable by changing the term |V ⋅ N| to |V ⋅ N|α, where α is a controllable parameter.
| α = 0.3 | α = 0.6 | α = 1 |
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In these shaders I have implemented both traditional normal mapping based on a texture with a set of normal vectors baked onto it, as well as a single-step parallax shader which uses both the baked normal map as well as a height map used to shift which texel is loaded from the normal map. Both are implemented as per-pixel shaders and the reflectance model used is Phong.
| Normal mapping | Single-step Parallax mapping |
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This is a simple toon shader demonstrating a non-photorealistic reflectance model. The shader uses two different colours for the lit and unlit diffuse, as well as a color for the outline of the object and a color for the specular highlights. The thickness of the outlines can be controlled through a parameter. However, the model results in differnt size outlines around the object, and works primarily for smooth objects.
| Toon shader, with 2 diffuse colors |
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This shader implements a cool little effect that is used in different games, when e.g. burning a paper or if an object dissolves. The shader compares an input parameter, γ with values in a Perlin noise map, and as the input parameter goes from 1 to 0, the object mesh becomes more and more transparent. To give the effect of burning edges, a "burn gradient" map is used, which stores the color of the edges and their alpha value, resulting in the edges fading out.
| γ = 0 | γ = 0.3 | γ = 0.6 | γ = 0.75 |
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This shader shows different screen effects, implemented through Unity’s Image Effect shaders. It uses a vignette, noise and scanline map, where each adds to a different part of the overall feel. The vignette map is a static effect, while the noise and scanline are dynamic with adjustable speeds. Furthermore, the color tint and the contrast and brightness of the cameras output can be adjusted.
| Night vision image effect with: contrast = 2 and brightness = 0.5 |
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Aside from working with real-time graphics, I have also implemented the ray tracers described by Pete Shirleys "Ray Tracing Minibooks" E-book series, in C++. I have however not included the code on my repository due to it not making any considerable changes to the Shireley’s own publicly available repository. I have also started looking into implementing a ray tracer based on the book "Physically Based Rendering" by Matt Pharr, Wenzel Jakob and Greg Humphreys, but have nothing to showcase so far.