Image synthesis and OpenGL: exercices 06

Setup

• OpenGL: Open Graphics Library (online spec, pdf spec)
• GLU: OpenGL Utility Library
  
• GLEW: OpenGL Extension Wrangler Library
  
• GLM: OpenGL Mathematics library
• QT: the window manager
  

1. Download the sources at http://romain.vergne.free.fr/teaching/IS/data06/TP06.tgz
2. If needed, edit the file main.pro to change paths
3. To compile: qmake && make
   
4. To run: ./tp06 file.off
   
5. To edit: use either your preferred text editor or qtcreator
   

Appearance and details

Exercise 1: texture mapping

• one shader has been added to the system (called texture-mapping.{vert,frag} and performs a Phong shading using the Phong model.
• uv coordinates are already sent to the shader, as well as the tangents
• the shader multiplies the diffuse component of the BRDF by the color of an input texture to obtain a textured shading
  

1. In the viewer, create 2 other textures (in the function createTextures as before)
• a specular texture ("textures/chesterfield-specular.png") that controls where highlights should have a lot of importance
• an ambient occlusion texture ("textures/chesterfield-ao.png") that approximates global illumination effects (cavity shadowing)
• Note: the principle is the same as with the color texture. You will have to modify the following functions
• createTextures
• deleteTextures
• enableShaders
• and of course the shader themselves
2. In the fragment shader, obtain the desired result
   
• Note 1: color is usually multiplied with the diffuse lighting intensity (already done)
  
• Note 2: ambient occlusion should be multiplied with the final resulting color
  
• Note 3: the specular map could either control the shininess (the specular exponent) or the specular intensity
  

Exercise 2: normal mapping

1. Create a new shader called normal-mapping.vert/frag (function createShaders)
2. Create a new texture ("textures/chesterfield-normal.png"), and send it the shader
   
3. In the fragment shader compute the TBN matrix (the binormal is computed from the normal and the tangent)
4. Use this TBN matrix to transform the normal (obtained from the normal map) from tangent to the camera space
1. Note: the normal was remapped in the range [0,1] in order to be able to be stored in the texture
2. You thus need to remap it in the range [-1,1] before use.
   
5. Use this modified new normal to compute the shading

Exercise 3: environment mapping

1. Create a new shader called environment-mapping.vert/frag (function createShaders)
2. Create a new texture ("textures/env1.jpg" - or env2.jpg or env3.jpg), and send it the fragment shader
3. Create the conversion function from a 3D vector \( \mathbf{r} \) to a 2D coordinate \( (u,v) \) and use it to access the texture
   
• \( u = \frac{atan(r_x,r_z)+\pi}{2\pi} \)
• \( v = \frac{acos(-r_y)}{\pi} \)
4. What kind of effect do you obtain when used with
   
1. the normal vector (in world space - you may send it to the fragment shader)?
2. the normal vector (in camera space)?
3. the refracted view vector (refraction between the eye and the normal)?
   
4. the reflected view vector (reflection between the eye and the normal)?

BONUS

Exercise 4: displacement mapping

1. Create a new shader called displacement-mapping.vert/frag - simply copy the normal-map one (function createShaders)
2. Create a new texture ("textures/chesterfield-height.png"), and send it the (vertex) shader
3. Displace the vertex position towards the direction of its normal, according to the height value to obtain the displacement effect
• Note: the normal should be perturbed with the normal mapping technique, as in exercise 2
  

Exercise 5: combination of effects

1. Create a new shader called full-mapping.vert/frag (function createShaders)
2. Activate and combine
   
• the normal mapping technique
• the displacement mapping technique
  
• the phong illumination
  
• the reflection illumination
3. Note: combine Phong and mirror reflection according to the surface angle (according to the line of sight)