Shadow Techniques for Real-Time and Interactive Applications

Shadow Techniques for Real-Time and Interactive Applications Stefan Brabec Promotionskolloquium MPI Informatik, Saarbrücken, Germany 3.2.2004

Importance of Shadows ,[object Object],[object Object],[object Object],[object Object],[object Object],Leonardo Da Vinci

Shadows in Computer Graphics ,[object Object],[object Object]

Shadows in Computer Graphics ,[object Object],[object Object],Discontinuity Meshing [Heckbert92]

Shadows for Real-Time Applications ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Doom3

Shadows for Interactive Applications ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],SolidWorks

Shadows for Non-Interactive Applications ,[object Object],[object Object],[object Object],Maya Software Maya OpenGL

Computing Shadows ,[object Object],[object Object],[object Object],[object Object],[object Object]

Related Work ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Shadow Mapping [Williams78] ,[object Object],[object Object],[object Object],[object Object]

Shadow Mapping ,[object Object],[object Object],[object Object],[object Object],[object Object]

Shadow Mapping ,[object Object],Blocky shadow edges due to limited shadow map resolution

Improve Sampling Rate ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Practical Shadow Mapping ,[object Object],[object Object],[object Object],[object Object]

Practical Shadow Mapping ,[object Object],[object Object],[object Object],[object Object],map regions used regions new map frustum

Practical Shadow Mapping optimized shadow map normal shadow map

Practical Shadow Mapping ,[object Object],[object Object],Self shadowing Missing shadows

Practical Shadow Mapping ,[object Object],z-range relevant z-range Normal approach: Near & far plane encloses all objects ! Better: Near & far plane encloses all from camera visible objects !

Practical Shadow Mapping ,[object Object],[object Object],0 range used 1

Practical Shadow Mapping ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Practical Shadow Mapping ,[object Object],[object Object],[object Object],Red: original distribution Green: normalized distribution z

Practical Shadow Mapping ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Shadow Mapping ,[object Object],[object Object],[object Object],[object Object]

Dual-Paraboloid Shadow Mapping ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Dual-Paraboloid Shadow Mapping ,[object Object],[object Object],[object Object],[object Object],[object Object]

Dual-Paraboloid Shadow Mapping ,[object Object],first hemisphere second hemisphere final image with two shadow maps applied 1 2 3

Dual-Paraboloid Shadow Mapping ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Shadow Volumes [Crow77] ,[object Object],[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 Rendering ,[object Object],[object Object]

Shadow Volume Rendering ,[object Object],[object Object],initialize z-buffer shadow volumes light contribution ambient contribution repeat for all lights final image

Combined Shadow Mask ,[object Object],[object Object],repeat shadow volumes L i shadow volumes L i+1 shadow volumes L i+N shadow mask light contribution L i ....L i+N times

Combined Shadow Mask ,[object Object],[object Object],[object Object],[object Object]

Combined Shadow Mask ,[object Object]

Combined Shadow Mask ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],-X +X -Z +Z +Y -Y

Combined Shadow Mask ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

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

Shadow Volume Generation ,[object Object],[object Object],[object Object],[object Object],Mesh as seen by light source Silhouette

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

Shadow Volume Generation ,[object Object]

Silhouette Detection on GPU ,[object Object],[object Object],[object Object],[object Object],[object Object]

Silhouette Detection on GPU ,[object Object],[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.

Silhouette Detection on GPU ,[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

Silhouette Detection on GPU ,[object Object],[object Object],[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();

Silhouette Detection on GPU ,[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

Shadow Volume Rendering ,[object Object],[object Object],[object Object],[object Object],[object Object],P 0 L P 3 P 0- L P 3- L

Shadow Volumes on GPU ,[object Object]

Shadow Volumes on GPU ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Soft Shadow Techniques ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Soft Shadow Maps ,[object Object],[object Object],[object Object],[object Object],Point Light Source Linear Light Source

Soft Shadow Maps ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Soft Shadow Maps ,[object Object],[object Object],[object Object]

Soft Shadow Maps ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Soft Shadow Maps ,[object Object],depth map edge detection triangulate render+shade visibility map to 3D warp

Soft Shadow Map Algorithm shade(p) { if( depth 1 (p) > S 1 [p] ) l 1 = 0; else l 1 = V 1 [p] * illum(p,L 1 ); if( depth 2 (p) > S 2 [p] ) l 2 = 0; else l 2 = V 2 [p] * illum(p,L 2 ); return l 1 +l 2 ; } S 1 V 1 S 2 V 2

Soft Shadow Maps ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Single Sample Soft Shadows ,[object Object],[object Object]

Single Sample Soft Shadows ,[object Object],[object Object],[object Object]

Single Sample Soft Shadows ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Single Sample Soft Shadows ,[object Object],[object Object],[object Object],[object Object]

Single Sample Soft Shadows ,[object Object],[object Object],[object Object],[object Object],[object Object],maximal extend hard shadow found

Single Sample Soft Shadows ,[object Object],[object Object],P ` r m a x 2 r m a x 1 depth map search larger penumbra

Single Sample Soft Shadows ,[object Object],[object Object],[object Object],[object Object],[object Object],larger penumbra

Single Sample Soft Shadows ,[object Object],[object Object],[object Object],c is user defined constant where inner and outer meet (e.g. 0.5) f  [0.0;c) f  [c;1.0] Attenuation depth_light[…] – depth_light[P` x , P` y ] P` z - depth_light[…] r`max = rmax * lit pixels blocked pixels Search for pixel is blocked pixel is lit Search when Inner Penumbra Outer Penumbra

Single Sample Soft Shadows ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],~20 fps (P4 + GF4) Light depth map: 512x125 Window resolution: 512x512

Single Sample Soft Shadows ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Conclusions & Future Work ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Shadow Techniques for Real-Time and Interactive Applications

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Shadow Techniques for Real-Time and Interactive Applications