Practical assignment #2

Assignment presentation

• Prepare a 2 min video presenting your software;
• Share the link to your GIThub repo through this form;
• The practical assignment has to reside in a branch named PA2.

Requirements

    Use sources from PA#1 adding a new functionality as follows:

• Render the surface with filled triangles using VBO (Vertex Buffer Object) technology with indices;
• Add two sliders providing ability to control surface granularity over U and V directions;
• Implement triangle shading method as per variant;
• Implement vertex and pixel shaders that calculate intensity of illumination for the surface coming from a single light source: I_rgb=Ambient+Diffuse+Specular that rotates in a circle motion around the surface. 

Resources

    The project we started to code at the lecture is here WebGL PA2

Details on Normals Calculation

• Analytic normal: implement the function calculating tangent vectors along U and V directions of your surface; to calculate the normal take the cross product of two surface tangents and normalize the result;
• Facet Average normal: sum all facet normals that are adjacent to the vertex to form a vertex normal, normalize the result;
• Facet Weighted Average normal: sum all facet normals that are adjacent to the vertex to form a vertex normal observing weight, normalize the result;
• pass the vertex normals as vertex attributes to GPU.

Details on Flat/Gouraud/Phong shading

    Implement the necessary code in .js and/or vertex/fragment shader.

Details on a Local light source

• pass coordinates of a light source to GPU as uniform parameter;
• do not forget to multiply the coordinates by ModelView matrix before passing them to GPU.

Details on projection

    use single point perspective/orthographic matrix.

Hint

• when calculating specular component you can take (0,0,1) direction vector as the vector pointing towards the viewer instead of calculating per-pixel direction (global viewer model);
• intensity of the light source components can be hardcoded in the shader;
• you can calculate the world coordinates of each point in fragment shader  interpolating vertex coordinates using hardware interpolator (varying keyword);
• If you need to interpolate normals along primitive pass them to fragment shader using varying keyword.

Variant*		Shading Gouraud	Shading Flat	Shading Phong		Normal Analytic	Normal Facet average	Normal Facet Weighted average
1		V				V
2			V			V
3				V		V
4		V					V
5			V				V
6				V			V
7		V						V
8			V					V
9				V				V
10		V				V
11			V			V
12				V		V
13		V					V
14			V				V
15				V			V
16		V						V
17			V					V
18				V				V
19		V				V
20			V			V
21				V		V
22		V					V
23			V				V
24				V			V
25		V						V
26			V					V
27				V				V
28		V				V
29			V			V
30				V		V

*Variants higher than 30 start counting from 1