CS425 OpenGL Materials

What Color Is It? green & blue absorbed white light Looks red

What Color Is It? red & blue absorbed white light Looks green

What Color Is It? blue absorbed white light Looks yellow

What Color Is It? red absorbed red light ? cyan

What Color Is It? red absorbed red light cyan Looks black

What Color Is It? blue absorbed magenta light ?

What Color Is It? blue absorbed magenta light Looks red

Material Response to Light The material specified in OpenGL can have three different responses to the light hitting it plus one emissive characteristic. You can separately specify the response to: –Ambient –Diffuse –Specular And you can specify that the material “emits light”

glMaterial{if}v(face, pname, param) face –GL_FRONT –GL_BACK –GL_FRONT_AND_BACK

glMaterial{if}v(face, pname, param) pname –GL_AMBIENT (ambient color of material) –GL_DIFFUSE (diffuse color of material) –GL_AMBIENT_AND_DIFFUSE (both) –GL_SPECULAR (specular color of material) –GL_SHININESS (specular exponent) –GL_EMISSION (emissive color of material) –GL_COLOR_INDEXES (ambient, diffuse, and specular color indices)

glMaterial{if}v(face, pname, param ) param The value for the pname’d material property Example GLfloat mat_amb_diff [ ] = {0.1, 0.5, 0.8, 1.0}; glMaterialfv( GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, mat_amb_diff);

NO Ambient (.7,.7,.7) Ambient (.8,.8,.2) Ambient Diffuse only (.1,.5, ) diffuse & specular (low shininess) diffuse & specular (high shininess) + (.3,.2,.2,.0) emmissive, no specular specular (1,1,1,1) shininess (5.0) specular (1,1,1,1) shininess (100.0)

Nate Robbins Lightmaterial

Color Material Mode I didn’t find this previously. Causes the material property specified to track the value of the current color (glColor*) glColorMaterial(face, mode) “face” and “mode” are same as for glMaterial. Must use glEnable (see example)

glColorMaterial example glEnable(GL_COLOR_MATERIAL); glColorMaterial(GL_FRONT, GL_DIFFUSE); glColor3f(0.2, 0.5, 0.8); /* draw some objects */ glColorMaterial(GL_FRONT, GL_SPECULAR); /*glColor no longer changes diffuse reflection, it now changes secular reflection */ glColor3f(0.9, 0.0, 0.2); /* draw some other objects */ glDisable(GL_COLOR_MATERIAL);

colormat.c

Two Sided Materials GLfloat outside = {0.2, 1.0, 1.0, 1.0}; GLfloat inside = {1.0, 0.5, 0.5, 1.0}; … glMaterialfv(GL_FRONT, GL_DIFFUSE, outside); glMaterialfv(GL_BACK, GL_DIFFUSE, inside); … glLightModelf(GL_LIGHT_MODEL_TWO_SIDE, GL_TRUE);

Additional Clipping Plane GLdouble eqn[ ] = {0.0, -1.0, 0.07, 0.5}; … glEnable(GL_CLIP_PLANE0); … glClipPlane(GL_CLIP_PLANE0, eqn); ABCD Plane equation See cutting.c (handout)

Two Sided Materials with Cutting Plane

OpenGL Attenuation Same formula that Denbigh gave. c = constant factor l = linear factor q = quadratic factor d = distance

Function Calls You use the glLightf function to select attenuation factors. Default values are kc=1, kl=0, kq=0. –glLightf(GL_LIGHT0, GL_CONSTANT_ATTENUATION, 2.0); –glLightf(GL_LIGHT0, GL_LINEAR_ATTENUATION, 0.0); –glLlightf(GL_LIGHT0, GL_QUADRATIC_ATTENUATION, 0.0);

kc=1 kl=0 kq=0 kc=0 kl=1 kq=0 kc=0 kl=0.5 kq=0 kc=0 kl=0.2 kq=0 kc=0 kl=0.1 kq=0 kc=0 kl=0.01 kq=0 kc=0 kl=0 kq=0.1 kc=0 kl=0 kq=0.001 kc=1 kl=0 kq= =