* Convert from object to world co-ordinates, then camera space and finally clip space. * We workout vertex normals, for lighting
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What happens in clipping?
Get rid of anything that is not in the view of the eye. We create a frustum of what we can see to do this, and then do clipping for each plane of the frustum (6 times)
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What is point-plane clipping?
We do the dot product with the plane normal and the point vector, if it is positive it is outside.
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What happens in rasterisation?
We turn primitives into pixels, for each pixel we work out whether it is a triangle or not, this is called scan conversion
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What happens in fragment processing?
This is where we compute the final fragment colours and shading, based on the texture mapping and lighting computations
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What happens in frame buffer processing?
For every pixel we work out which fragment, or combination of fragments to use based of which is in front.
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What are the painter’s and z-buffer algorithm
Painter’s algorithm, order all objects, paint from back to front overpainting when there’s a close object.
Z-buffer store the closest depth for each pixel, initially infinity then when drawing comprae new depth to this depth and paint if lower.
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What is a pure diffuse reflection?
The surface scatters light equally in all directions.
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What is a pure mirror reflection?
Line reflects along a line symmetrical about the surface normal
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What are the three tpyes of lighting in the phon model?
diffuse reflectivity x light source intensity x cos angle (between light and surface normal)
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How do we workout specular reflection?
specular reflectivity x light source intensity x cos angle (netween viewing ray and reflected ray ^ shininess coefficent.
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What is the shininess coefficent
This describes the breadth of the angle of specular reflection, basically how much of an angle the viewing ray can be and still see the reflected ray. If this is smaller we have a broader angle and rougher objects. If this is larger we have a narrower angle and a smoother surface.
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How do we workout ambient lighting?
ambient reflectivity x light source intensity
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What can we replace cosine with for vector arithmetic?
Dot product of vectors, i.e theta is (l normal), phi is (reflection, viewing)^alpha
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What are the different shading models, and how do they calculate light?
* Flat shading, per polygon * Gourad shading, per vertex * Phong shading, per pixel.
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What do we call a model that uses a 4D function based on measurement to workout how much light is reflected?
Bidirectional reflectance distributions function (BRDF)
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What are subsurface effects?
For translucent objects you have to work out the way light rays are absorbed, reflected inside and re-emited
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What is a texture?
An image applied to a surface.
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What are the two interpretations for workout out what part of the texture we want?
Forward and backward mapping (with bilinear interpolation)
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What is bump mapping?
Where you perturb the surface normal to make it look bump.
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What is displacement mapping?
Perturbing the surface height to physically change the shape of the object
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What is environment mapping?
Surround the scene with a sphere, render the scene onto the sphere and colour the surface by reflection.
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What are mipmaps?
Set of downsampled images of a texture, we choose fidelity basd on distance and move co-ordinates to get the right one.
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What do we need to fit two polynomail curves together?