1. Joshua Barczak* CMSC 435 UMBC
Renderman
Joshua Barczak*
CMSC 435
UMBC
* Sample code stolen verbatim from Dr. Marc Olano

2. Project Goals Introduce some concepts Develop spatial reasoning skills
Lights,Models,Materials,Transforms
Common themes in graphics systems
Some context for what’s ahead
Develop spatial reasoning skills
Feel the pain of artists

3. What RenderMan Is RenderMan Open Interface specification for renderers
Renderman Interface Bytestream (RIB)
C Binding
Programmable shader language

4. RenderMan C Interface used to describe scene Light Sources
Camera Parameters
Objects
Geometric Shape
Visual Appearance
Transformations

5. Transformations RiTranslate RiRotate RiScale Move Stuff
Rotate the world
RiScale
Make the world bigger or smaller

6. Project 1 Dev Cycle Do: Until 11:59PM on due date
Write C code
Compile, linking with libri  executable
run program RIB
rndr  TIFF file
Display image
Contemplate ramifications of image
Until 11:59PM on due date
Check your code in! (see website)

7. The Universe According to RenderMan
You need to tell it where all this stuff is
Y Axis
Z Axis
0,0,0
You are here…
X Axis

8. Minimal RenderMan Program
#include "ri.h"
RtPoint Square[4]={{.5,.5,.5},{.5,-.5,.5},{-.5,.5,.5},{-.5,-.5,.5}};
static RtColor Color = {.2, .4, .6};
int main () {
RiBegin("square.rib"); /* start the renderer */
RiDisplay("square.tif","file","rgb",RI_NULL);
RiWorldBegin();
RiSurface ("constant", RI_NULL);
RiColor (Color); /* declare color */
RiPatch (RI_BILINEAR, /* declare the square */
RI_P, (RtPointer) Square, RI_NULL);
RiWorldEnd();
RiEnd();
return 0; }
NOTE: Variable arguments…

9. square.rib ## Pixie 2.2.4 ## Generated Sat Jan 26 14:11:14 2013
Display "square.tif" "file" "rgb"
WorldBegin
Surface "constant"
Color [ ]
Patch "bilinear" "P" [ ]
WorldEnd

10. square.tif

11. Refined Program Add a light… #include "ri.h"
RtPoint Square[4]={{.5,.5,.5},{.5,-.5,.5},{-.5,.5,.5},{-.5,-.5,.5}};
static RtColor Color = {.2, .4, .6};
int main () {
RiBegin("persp.rib"); /* start the renderer */
RiDisplay("persp.tif","file","rgb",RI_NULL);
RiLightSource ("distantlight", RI_NULL);
RiProjection("perspective", RI_NULL);
RiTranslate(0.0,0.0,1.0);
RiRotate (40.0, -1.0, 1.0, 0.0);
RiWorldBegin();
RiSurface ("matte", RI_NULL);
RiColor (Color); /* declare color */
RiPatch (RI_BILINEAR, /* declare the square */
RI_P, (RtPointer) Square, RI_NULL);
RiWorldEnd();
RiEnd();
return 0; }
Add a light…

12. Refined Program Tell it to shrink stuff with distance… #include "ri.h"
RtPoint Square[4]={{.5,.5,.5},{.5,-.5,.5},{-.5,.5,.5},{-.5,-.5,.5}};
static RtColor Color = {.2, .4, .6};
int main () {
RiBegin("persp.rib"); /* start the renderer */
RiDisplay("persp.tif","file","rgb",RI_NULL);
RiLightSource ("distantlight", RI_NULL);
RiProjection("perspective", RI_NULL);
RiTranslate(0.0,0.0,1.0);
RiRotate (40.0, -1.0, 1.0, 0.0);
RiWorldBegin();
RiSurface ("matte", RI_NULL);
RiColor (Color); /* declare color */
RiPatch (RI_BILINEAR, /* declare the square */
RI_P, (RtPointer) Square, RI_NULL);
RiWorldEnd();
RiEnd();
return 0; }
Tell it to shrink stuff with distance…

13. Refined Program
#include "ri.h"
RtPoint Square[4]={{.5,.5,.5},{.5,-.5,.5},{-.5,.5,.5},{-.5,-.5,.5}};
static RtColor Color = {.2, .4, .6};
int main () {
RiBegin("persp.rib"); /* start the renderer */
RiDisplay("persp.tif","file","rgb",RI_NULL);
RiLightSource ("distantlight", RI_NULL);
RiProjection("perspective", RI_NULL);
RiTranslate(0.0,0.0,1.0);
RiRotate (40.0, -1.0, 1.0, 0.0);
RiWorldBegin();
RiSurface ("matte", RI_NULL);
RiColor (Color); /* declare color */
RiPatch (RI_BILINEAR, /* declare the square */
RI_P, (RtPointer) Square, RI_NULL);
RiWorldEnd();
RiEnd();
return 0; }
Tell it what to do to the world so it lines up to the camera…

14. The Universe According to RenderMan
RenderMan’s coordinates…
X Axis
Y Axis
Z Axis
“World” Coordinates

15. Refined Program This means:
#include "ri.h"
RtPoint Square[4]={{.5,.5,.5},{.5,-.5,.5},{-.5,.5,.5},{-.5,-.5,.5}};
static RtColor Color = {.2, .4, .6};
int main () {
RiBegin("persp.rib"); /* start the renderer */
RiDisplay("persp.tif","file","rgb",RI_NULL);
RiLightSource ("distantlight", RI_NULL);
RiProjection("perspective", RI_NULL);
RiTranslate(0.0,0.0,1.0);
RiRotate (40.0, -1.0, 1.0, 0.0);
RiWorldBegin();
RiSurface ("matte", RI_NULL);
RiColor (Color); /* declare color */
RiPatch (RI_BILINEAR, /* declare the square */
RI_P, (RtPointer) Square, RI_NULL);
RiWorldEnd();
RiEnd();
return 0; }
This means:
Rotate THEN translate. (It’s like a stack) This will be extremely confusing….
There are reasons for this, but they are still many lectures out…

16. Refined Program RiWorldBegin resets the stack… #include "ri.h"
RtPoint Square[4]={{.5,.5,.5},{.5,-.5,.5},{-.5,.5,.5},{-.5,-.5,.5}};
static RtColor Color = {.2, .4, .6};
int main () {
RiBegin("persp.rib"); /* start the renderer */
RiDisplay("persp.tif","file","rgb",RI_NULL);
RiLightSource ("distantlight", RI_NULL);
RiProjection("perspective", RI_NULL);
RiTranslate(0.0,0.0,1.0);
RiRotate (40.0, -1.0, 1.0, 0.0);
RiWorldBegin();
RiSurface ("matte", RI_NULL);
RiColor (Color); /* declare color */
RiPatch (RI_BILINEAR, /* declare the square */
RI_P, (RtPointer) Square, RI_NULL);
RiWorldEnd();
RiEnd();
return 0; }
RiWorldBegin resets the stack…
There are reasons for this, but they are still many lectures out…

17. Spheres Fiddle with these and watch what happens… #include "ri.h"
RtFloat radius=1.0, zmin=-1.0, zmax=1.0, thetamax=360;
int main () {
RiBegin("sphere.rib"); /* start the renderer */
//…
RiWorldBegin();
// …
RiSphere (radius, zmin, zmax, thetamax, RI_NULL);
RiWorldEnd();
RiEnd();
return 0; }

18. Other Stuff That’s in There
RiCylinder
RiParaboloid
RiCone
RiHyperboloid
RiSphere
RiTorus
And much MUCH more I don’t have time for. RiRTM() 

19. Unit Cube #include "ri.h" static RtColor Color = {.2, .4, .6};
void UnitCube() {
/* ???? */ }
int main ()
RiBegin("cube.rib"); /* start the renderer */
// …
RiWorldBegin();
UnitCube();
RiWorldEnd();
RiEnd();
return 0;

20. Unit Cube #define L -.5 #define D -.5 #define N -.5
#define R .5 #define U .5 #define F .5
void UnitCube () {
static RtPoint Cube[6][4] = {
{{L,D,F}, {R,D,F}, {R,D,N}, {L,D,N}}, // bottom
{{L,D,F}, {L,U,F}, {L,U,N}, {L,D,N}}, // left
{{R,U,N}, {L,U,N}, {L,U,F}, {R,U,F}}, // top
{{R,U,N}, {R,U,F}, {R,D,F}, {R,D,N}}, // right
{{R,D,F}, {R,U,F}, {L,U,F}, {L,D,F}}, // far
{{L,U,N}, {R,U,N}, {R,D,N}, {L,D,N}}};//near
int i;
for (i = 0; i < 6; i++) {
RiPolygon(4,RI_P,(RtPointer)Cube[i],RI_NULL); }} 1
RiPolygon Vertices in this order… 3 2

21. Transforming Objects RiColor (Blue); UnitCube(); RiColor(Yellow);
RiTransformBegin();
RiTranslate( 2, 0, 0 );
RiRotate( 30.0, 0, -1, 0 );
RiTransformEnd();
RiColor(Red);
RiTranslate( -2, 1, 0 );
RiRotate(-60,0,1,0);
RiScale( 2, 0.5, 1 );
Push current transformation state….
Return to state at last TransformBegin()
You can nest these things if you want, consider the implications…

22. Transforming Objects RiColor (Blue); UnitCube(); RiColor(Yellow);
RiTransformBegin();
RiTranslate( 2, 0, 0 );
RiRotate( 30.0, 0, -1, 0 );
RiTransformEnd();
RiColor(Red);
RiTranslate( -2, 1, 0 );
RiRotate(-60,0,1,0);
RiScale( 2, 0.5, 1 );
Save state
Move the origin by that much
Rotate the coordinate system
Put axis-aligned unit cube at the origin
Go back
The transform calls are interpretted differently during WorldBegin/End than they are outside of it. This can be extremely confusing…

23. Transforming Objects RiColor (Blue); UnitCube(); RiColor(Yellow);
RiTransformBegin();
RiTranslate( 2, 0, 0 );
RiRotate( 30.0, 0, -1, 0 );
RiTransformEnd();
RiColor(Red);
RiTranslate( -2, 1, 0 );
RiRotate(-60,0,1,0);
RiScale( 2, 0.5, 1 );
RiScale means: Change size by this much on each axis…
Try reversing the order and watch what happens…

24. Transforms

25. Another Cube RiPatch Vertices in this order… 2 1 3
RtPoint Square[4]={{.5,.5,.5},{.5,-.5,.5},{-.5,.5,.5},{-.5,-.5,.5}};
static RtColor Color = {.2, .4, .6};
void UnitCube () {
RiTransformBegin();
RiPatch(RI_BILINEAR,RI_P,(RtPointer)Square, RI_NULL);
RiRotate(90.0, 0.0, 1.0, 0.0); // right face
RiRotate(90.0, 0.0, 1.0, 0.0); // near face
RiRotate(90.0, 0.0, 1.0, 0.0); // left face
RiTransformEnd();
RiTransformBegin(); // bottom face
RiRotate(90.0, 1.0, 0.0, 0.0);
RiTransformBegin(); // top face
RiRotate(-90.0, 1.0, 0.0, 0.0); }
RiPatch Vertices in this order… 2 1 3

26. Light Sources DistantLight Like the sun Parameters From/To LightColor
Intensity

27. DistantLight

28. DistantLight RtFloat from[] = { -1,1,0.2}; RtFloat to[] = { 0,0,0 };
RiLightSource ("distantlight", "from", from, "to", to, RI_NULL);

29. DistantLight RtFloat from[] = { 1,1,0.2}; RtFloat to[] = { 0,0,0 };
RiLightSource ("distantlight", "from", from, "to", to, RI_NULL);

30. DistantLight RtFloat from[] = {1,1,0.2}; RtFloat inten = 5;
RiLightSource ("distantlight", "from", from, "intensity", &inten, RI_NULL);

31. DistantLight RtFloat from[] = {1,1,0.2}; RtFloat inten = 5;
RiLightSource ("distantlight", "from", from, "intensity", &inten, RI_NULL);

32. PointLight Like a light bulb lightcolor intensity “from” (where is it)
Brightness radiates outwards, falls off with distance
Should always set intensity

33. PointLight RtFloat from[] = { 0,0,3 }; RtFloat intensity=5;
RiLightSource( "pointlight", "from", from, "intensity", &intensity, RI_NULL );

34. PointLight RtFloat from[] = { 0,0,3 }; RtFloat intensity=10;
RiLightSource( "pointlight", "from", from, "intensity", &intensity, RI_NULL );

35. PointLight RtFloat from[] = { 0,1,3 }; RtFloat intensity=10;
RiLightSource( "pointlight", "from", from, "intensity", &intensity, RI_NULL );

36. Materials Matte Plastic Things that aren’t too shiny
Kd: How bright it looks (0-1)
Plastic
Shiny coating with matte underneath
Kd: Same as matte
Ks: How bright the shine is
roughness: How shiny it looks
1  Looks like matte
 Mirror

37. Materials Plastic Spheres Roughness 0.01, 0.1, 0.5 RtFloat Kd = 0.8f;
RtFloat rough = 0.01f;
RiSurface ("plastic", "Kd", &Kd, "roughness",&rough, RI_NULL);

38. Materials Metal PaintedPlastic/PaintedMatte Raytraced surfaces
Basically plastic, without the matte underneath
PaintedPlastic/PaintedMatte
Use an image texture for color
Raytraced surfaces
Glass, Mirror
CD to $PIXIEHOME/shaders and look around…