1. RenderMan Jae Woo Kim Doctoral Student, Institute for Computer Graphics The George Washington University

2. The Goal of Today

3. What is RenderMan • API for graphics rendering • Designed by Pixar in 1988 • Photosurrealistic Rendering • Used in many movies with digital effects • Shading Language • Flexibility for complex digital effects • Many RenderMan compliant Renderers

4. RenderMan compliant Renderers • PhotoRealistic RenderMan (PRMan) • by Pixar • $5,000 per cop • Blue Moon Rendering Tools (BMRT) • Made by Dr. Larry Gritz • Maintained by Exluna Inc. • Free for non-commercial use ( until last year I guess … )

5. Comparison: RenderMan vs. OpenGL / DirectX

6. RenderMan vs Commercial packages

7. Rendering Overview Application Program RenderMan compliant Renderer Scene Description (RIB format) Shading Requests / Results Shading Requests / Results User-defined Shading Modules Standard Shading Modules

8. Application Program • All API calls starts with Ri prefix • All API calls generate RIB(RenderMan Interface Bytestream) output RiAttributeBegin (); RiTranslate (0.0, 14.0, -8.3); RiSufrace (“plastic”, RI_NULL); RiSphere (1.0, -1.0, 1.0, 360.0, RI_NULL); RiAttributeEnd (); RiAttributeBegin (); RiTranslate (0.0, 14.0, -8.3); RiSufrace (“plastic”, RI_NULL); RiSphere (1.0, -1.0, 1.0, 360.0, RI_NULL); RiAttributeEnd (); AttributeBegin Translate 0.0, 14.0, -8.3 Sufrace “plastic” Sphere 1 –1 1 360 AttributeEnd AttributeBegin Translate 0.0, 14.0, -8.3 Sufrace “plastic” Sphere 1 –1 1 360 AttributeEnd

9. BMRT • Most widely used public domain RenderMan compliant renderer • Two versions of renderer • rgl: previewer based on OpenGL • rendrib: Photorealistic rendering with ray tracing / radiosity • Input: RIB stream • Output: image files or framebuffer

10. How to Install BMRT • Remove old version • Unpack BMRT distribution • Set BMRT environment variables • Test BMRT

11. Set MBRT Environment Variables • Right click, select properties • Select Advanced tab • Click Environment Variables • Set variables My Computer

12. The first very simple program

13. Listing 2.1 Geometry Light Surface property

14. Program Structure RiBegin() //Initialize RenderMan Interface RiLightSource("distantlight",RI_NULL ); RiWorldBegin() RiSurface("constant", RI_NULL ); RiPolygon( 4, RI_P, (RtPointer) square, RI_NULL ); RiWorldEnd() RiEnd() // End!!!

15. Define a polygon RiPolygon( 4, RI_P, (RtPointer) square, RI_NULL ); Last argument Terminating token The number of vertices Token-value pair: “An array of points giving positions in 3D space” RtPoint square[4] = { {.5,.5,.5 },{-.5,.5,.5}, {-.5,-.5,.5},{.5,-.5,.5} };

16. Define Surface Property RiSurface("constant", RI_NULL ); RiPolygon( … ); constant matte metal plastic Surface shaders … next week!

17. Define a light source RiLightSource("distantlight",RI_NULL ); Ambientlight Distantlight Pointlight spotlight Light source shaders … also next week!!

18. The second very simple program

19. Listing 2.2 Color Translation Rotation Perspective projection

20. Projection and Color RiProjection( "perspective", RI_NULL ); perspective orthographic static RtColor Color = { .2, .4, .6 }; R G B RiSurface( … ); RiColor(Color); RiPolygon( … );

21. Scope of Graphics Environment RiSurface( … ); RiColor(Color); RiPolygon( … ); RiPolygon( … ); RiColor(Color); RiPolygon( … ); • Affects all objects after it • Modifies the previous attribute

22. Graphics Environment Attributes of objects • Affects all objects after it • Modifies the previous attribute (not • for the transformations…) • Called before the object declaration • “Sticks to that object” • Default values (not for light sources) Transformations Color Light sources Surface properties Etc.

23. Geometric Transformations y x z RiTranslate( 0.0, 0.0, 1.0 ); Specify the motion along the x, y, z axes respectively RiRotate( 40.0, -1.0, 1.0, 0.0 ); A point in 3D space Amount of rotation In degrees Axis of rotation “Left handed rotation!!!”

24. The Order of Geometric Transformations RiTranslate()  RiRotate() RiRotate()  RiTranslate()

25. Geometric transformations accumulated! A B C D RiTranslate(-0.3,0.0,0.0); Object A; RiTranslate(-0.1,0.0,0.0); Object B; RiTranslate(0.1,0.0,0.0); Object C; RiTranslate(0.3,0.0,0.0); Object D; 0.3 - 0.3 - 0.1 0.1 - 0.3 0 - 0.4

26. The third very simple program

27. Six rectangles

28. Declare a Cube (1) A cube consists of six rectangles, so create six rectangles (Listing 2.3) Near, far, left, right, bottom, top defined in a function UnitCube( ) Problem: Readability – Difficult to read and understand

29. Declare a Cube (2) To use previously defined, simpler objects to createmore complex ones Cube is nothing but a set of squares in different positions and orientation Therefore, create six identical squares, and then transform each square to be located appropriate position in 3D space Click me: Listing 2.5

30. Declare Cube Square 1; /* RiPolygon( ) */ Rotate 90 degree; /* RiRotate( ) */ Square 2; Rotate 90 degree; Square 3; Rotate 90 degree; Square 4; Square 4 Square 3 Square 1 Square 2

31. Save and Restore Geometric Transformations Save current transform. RiTransformBegin(); Square 1; Square 2 rotated; Square 3 rotated; Square 4 rotated; RiTransformEnd(); RiTransformBegin(); Square 5; RiTransformEnd(); RiTransformBegin(); Square 6; RiTransformEnd(); Accumulated Restore current transform. Accumulated transform cleared!!

32. The fourth program – a little complicated … 

34. Cubes • A number of small cubes • R, G, B values of the cube vary with x, y, z coordinates • Near-lower-left corner is black, far-upper-right corner is • white • Each minicube given a color appropriate to its position • Inner loop of ColorCube( ) cycles n times through x, y, • z creating unit cubes, scaling them appropriately, then • translating them into position

35. Save and restore attributes • RiAttibuteBegin( ), RiAttributeEnd( ) • Save and restore all the attributes of the graphics environment • Not only geometric transformations RiAttributeBegin(); RiTransformBegin(); Transformations… Attributes … Objects … Objects… RiAttributeEnd(); RiTransformEnd();

36. Algorithm Loop x = 0 to n-1 Loop y = 0 to n-1 Loop z = 0 to n-1 Set color values; RiTransformBegin(); Transformations; Scale; Call UnitCube(); RiTransformEnd(); Listing 2.6

37. Primitive Surfaces Everything visible in a scene is ultimately composed of surfaces • Quadric Surfaces: Defined by quadric equations in two • dimensional space • Polygonal SurfacesBoundaries are given by a connected • series of line segments • Parametric Surfaces: Free form polynomial curved surfaces

38. Primitive Surfaces (I): Quadric Surfaces

39. Sphere Cone Cylinder Hyperboloid Paraboloid Torus

40. Quadric surfaces Finite curve in two dimensions is swept in three-dimensional space about one axis to create a surface Sphere Circle Torus Line segment, one end lying on the axis of rotation Cone Cylinder A line segment parallel to the axis Generalization of a line segment, By rotating an arbitrary line segment Hyperboloid Paraboloid Paraola y = x2

41. Sphere RiSphere(0.5, -0.5, 0.5, 360.0, RI_NULL); RiSphere(radius, zmin, zmax, thetamax, RI_NULL);

42. Cone RiCone(1.0, 0.5, 360.0, RI_NULL); RiSphere(height, radius, thetamax, RI_NULL);

43. Cylinder RiCylinder(0.5, -0.5, 0.5, 360.0, RI_NULL); RiCylinder( radius, zmin, zmax, thetamas, Parameterlist )

44. Hyperboloid RiHyperboloid(hyperpt1, hyperpt2, 360.0, RI_NULL); RiHyperboloid(point1, point2, thetamax, parameterlist);

45. Paraboloid RiParaboloid(0.5, 0.0, 0.9, 360.0, RI_NULL); RiParaboloid(rmax, zmin, zmax, thetamax, parameterlist);

46. Torus RiTorus(.4, .15, 0.0, 360.0, 360.0, RI_NULL); RiTorus(majorrad, minorrad, phimin, phimax, parameterlist);

47. Disk RiDisk(height, radius, thetamax, parameterlist);

48. Primitive Surfaces (II): Polygons

49. Polygons • A simple, easy-to use class of surface • Defined by boundary, given as an ordered series of vertices • Square in Listing 2.x RtPoint square[4] = { {.5,.5,.5 },{-.5,.5,.5}, {-.5,-.5,.5},{.5,-.5,.5} }; RiPolygon( 4, RI_P, (RtPointer) square, RI_NULL );

50. How to Use RIB Models RiWorldBegin (); RiSurface ("matte", RI_NULL); RiReadArchive("bench.rib", RI_NULL, RI_NULL); RiWorldEnd();