Shadow Volumes on Programmable Graphics Hardware

Shadow Volumes on Programmable Graphics Hardware Stefan Brabec Hans-Peter Seidel MPI Informatik

Overview ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Shadow Volumes ,[object Object],[object Object],[object Object],[object Object],[object Object]

Shadow Volumes ,[object Object],[object Object],[object Object],occluder light shadow region lit

Shadow Volume Generation ,[object Object],[object Object],[object Object],[object Object],[object Object]

Shadow Volume Generation ,[object Object],Light Light FF BF FF FF Silhouette Edge (v0,v1) ! No Silhouette Edge ! n 1 n 2 n 1 n 2

Shadow Volume Rendering ,[object Object],[object Object]

Shadow Volume Rendering ,[object Object],[object Object],[object Object],[object Object],[object Object],silhouette detection Focus of this talk:

Our method ,[object Object],[object Object],[object Object],[object Object],[object Object]

Input Data ,[object Object],[object Object],[object Object],Example: This is not a closed mesh, but since we are only focusing on one edge of this mesh its ok.

Coordinate Transformation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Transform to world/eye space ,[object Object],[object Object],[object Object],[object Object],P 0 P 1 P 2 P 3 P 4 position texture P 0 P 1 P 2 P 3 P 4 P N

Transform to world/eye space ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],!!ARBvp1.0 ATTRIB iVertexPos = vertex.position; ATTRIB iVertexIdx = vertex.texcoord[0]; PARAM mv[4] = { state.matrix.modelview }; OUTPUT oPos = result.position; OUTPUT oDumpPos = result.texcoord[0]; # Transform the vertex to eye coordinates . DP4 oDumpPos.x, mv[0], iVertexPos; DP4 oDumpPos.y, mv[1], iVertexPos; DP4 oDumpPos.z, mv[2], iVertexPos; DP4 oDumpPos.w, mv[3], iVertexPos; # Vertex position is its index (x,y,0,1) MOV oPos, iVertexIdx; END

Transform to world/eye space ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Process edges ,[object Object],[object Object],[object Object],[object Object],[object Object]

Process edges ,[object Object],[object Object],[object Object],E 0_idx P 0_idx P 1_idx P 3_idx P 4_idx glBegin(GL_POINTS) ; glAttrib(P0_idx, P3_idx, P1_idx, P4_idx); glVertex1f(E0_idx); glEnd();

Process Edges ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Process edges ,[object Object],E 0_idx P 0_idx P 1_idx P 3_idx P 4_idx input data 4 texture lookups for world space positions P 0 P 1 P 3 P 4 registers P 3 P 0 P 1 P 4 N 1 = (P 3 –P 0 )x(P 1 –P 0 ) N 2 = (P 4 –P 0 )x(P 3 –P 0 ) front & back facing ? position texture P 0 P 1 P 2 P 3 P 4 Light Store silhouette flag (yes/no) at edge index E 0 E 1 E 2 E 3 E 4 E M edge texture

Silhouette Detection ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Rendering Shadow Volumes ,[object Object],for all lights { for all edges { if (is silhouette edge for light i) { get edge’s vertices render extruded quad } } }

Rendering shadow volumes ,[object Object],[object Object],[object Object],[object Object],position texture P 0 P 1 P 2 P 3 P 4 P N E 0 E 1 E 2 E 3 E 4 E M edge texture glBegin(GL_QUADS) ; glVertex(P0_idx, E0_idx, 0); glVertex(P1_idx, E0_idx, 0); glVertex(P1_idx, E0_idx, 1); glVertex(P0_idx, E0_idx, 1); P = Lookup (p_idx) mask = Lookup (e_idx) if (mask & silhouette) { if (extrude) // 0 or 1 flag out = P – Light_pos else out = P } else { out = (0,0,0,1) // outside view }

Rendering shadow volumes ,[object Object],[object Object],E 0 = silhouette quad texture E` 0 = silhouette & extrude P 0 L P 3 P 0- L P 3- L Q 0 Q 1 Q 2 Q 3 Q 0 = (P 0x ,P 0y ,P 0z , E 0 ) Q 1 = (P 3x ,P 3y ,P 3z , E 0 ) Q 2 = (P 3x ,P 3y ,P 3z , E` 0 ) Q 3 = (P 0x ,P 0y ,P 0z , E` 0 )

Rendering Shadow Volumes ,[object Object],[object Object],[object Object],[object Object],[object Object],Light0: Silhouette Light0: Extrude Light1: Silhouette Light1: Extrude

Rendering Shadow Volumes ,[object Object],Vertex Array: glBegin(GL_QUADS) ; glArrayElement(0); glArrayElement(1); glArrayElement(2); glArrayElement(3); P_xyz = IN_xyz; E = IN_w; if(E & silhouette) { if(E & extrude) out = P-L; else out = P; } else { out = somewhere outside view } Q 0 Q 1 Q 2 Q 3

Rendering Shadow Volumes ,[object Object],[object Object],[object Object],[object Object],[object Object]

ARB_superbuffers ,[object Object],[object Object],[object Object],[object Object],[object Object],glVertexArrayMem ( GL_VERTEX_ARRAY, 4, mem, 0); memory block glAttachMem ( GL_DRAW_FRAMEBUFFER, GL_AUX0, mem); glAttachMem ( GL_TEXTURE_2D, GL_IMAGES, mem); glAllocMem2D (fmt, w, h, …)

ARB_superbuffers ,[object Object],[object Object],[object Object],[object Object],[object Object]

Summary ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Summary ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Summary ,[object Object],[object Object],[object Object],[object Object],[object Object]

Conclusions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Future Work ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Shadow Volumes on Programmable Graphics Hardware

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Shadow Volumes on Programmable Graphics Hardware