UW Extension Certificate Program in Game Development 2 nd quarter: Advanced Graphics

1. UW ExtensionCertificate Program inGame Development 2nd quarter:Advanced Graphics Lighting

2. Goals • Understand the general lighting problem • Review the classic lighting equation

3. The lighting equation

4. Approximating the equation • The general problem is intractable • We must construct approximate models • Models for light sources and for materials (reflection) • Multiple light sources are used simultaneously • Each light’s contribution calculated in isolation • Multiple models are used simultaneously • Each model handles just one aspect of light transfer • Apply all models to all lights • Add the results to combine them

5. The classic reflection models • Have been used for many years • Lambert’s diffuse lighting model: I=N•L • Non-reflective: no change with location of the viewer • Phong’s specular lighting model: I=(R•V)P • R=2(N•L)N - L • Reflective: changes as the viewer changes location • Specular model tends to be optional • I=observed light intensity • L=direction to the light • N=surface normal • V=direction to the viewer • R=reflection vector • P=specular power • L, N, V, R are normalized

6. The classic light source models • Each model returns: • How much light is received (RGB light intensity) • The L, used by the reflection model • Ambient light is just a constant RGB • Models light coming from everywhere (white noise) • Reflection model not applied (there’s no L) • Directional light has a constant RGB and L • Models the sun – light coming from very far away • Point and spot light use formulas for RGB and L

7. D3D lights • typedefstruct _D3DLIGHT9 { • D3DLIGHTTYPE Type; /* Type of light source */ • D3DCOLORVALUE Diffuse; /* Diffuse color of light */ • D3DCOLORVALUE Specular; /* Specular color of light */ • D3DCOLORVALUE Ambient; /* Ambient color of light */ • D3DVECTOR Position; /* Position in world space */ • D3DVECTOR Direction; /* Direction in world space */ • float Range; /* Cutoff range */ • float Falloff; /* Falloff */ • float Attenuation0; /* Constant attenuation */ • float Attenuation1; /* Linear attenuation */ • float Attenuation2; /* Quadratic attenuation */ • float Theta; /* Inner angle of spotlight cone */ • float Phi; /* Outer angle of spotlight cone */ • } D3DLIGHT9;

8. Material properties • The reflection models used are a material property • The specular power is also a material property • Coefficients are material properties, too • Ambient, diffuse, specular and emissive • Emissive is just added to the rest • Part of the material is applied in the pixel shader • The texture is just an ambient/diffuse coefficient! • Specular (and emissive) are added there, too

9. D3D materials • typedefstruct _D3DMATERIAL9 { • D3DCOLORVALUE Diffuse; /* Diffuse color RGBA */ • D3DCOLORVALUE Ambient; /* Ambientcolor RGB */ • D3DCOLORVALUE Specular; /* Specular 'shininess' */ • D3DCOLORVALUE Emissive; /* Emissive color RGB */ • float Power; /* Sharpness if specular highlight */ • } D3DMATERIAL9; • typedefenum _D3DMATERIALCOLORSOURCE • { • D3DMCS_MATERIAL = 0, // Color from material is used • D3DMCS_COLOR1 = 1, // Diffuse vertex color is used • D3DMCS_COLOR2 = 2, // Specular vertex color is used • D3DMCS_FORCE_DWORD = 0x7fffffff, // force 32-bit size enum • } D3DMATERIALCOLORSOURCE;

10. Implementation notes • Many 3D accelerators since the late 90’s have included hardware to perform all of this • D3D calls it the “fixed-function pipeline” • It’s completely removed in D3D10 • All of this must be done in shaders! • More flexibility = more work