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BATTLECAM™: A Dynamic Camera System for Real-Time Strategy Games

BATTLECAM™: A Dynamic Camera System for Real-Time Strategy Games. Yangli Hector Yee Graphics Programmer, Petroglyph hector@petroglyphgames.com Elie Arabian Lead Artist, Petroglyph elie@petroglyphgames.com. Overview. Background Theory Implementation Hacks Cinematic Shots

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BATTLECAM™: A Dynamic Camera System for Real-Time Strategy Games

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  1. BATTLECAM™: A Dynamic Camera System for Real-Time Strategy Games Yangli Hector Yee Graphics Programmer, Petroglyph hector@petroglyphgames.com Elie Arabian Lead Artist, Petroglyph elie@petroglyphgames.com

  2. Overview • Background • Theory • Implementation • Hacks • Cinematic Shots • Question & Answers

  3. Background – History • RTS Bird’s Eye (Dune 2) • First Person (Dungeon Keeper) • Scripted Actor & Camera (Warcraft 3) • Unscripted Actor, Unscripted Camera (Star Wars – Empire at War)

  4. Background - Problem • Make a ‘movie’ from an RTS battle • Actors can move during shot • Actors can die during shot • Players can move actors • Objects can move into camera

  5. Background - Solution • Pick most interesting object • Construct shot • Play shot • Fallback on death • Pick next object • Hijack existing camera scripting

  6. Theory – Visual Attention • How to pick ‘interesting object’ • Bottom Up: Stimulus • Intensity (black on white) • Motion (moving stuff) • Color (red on green) • Orientation (circle in stripes) • Top Down: Goals • Game Objectives • Current User Selection

  7. Feature Maps Image Intensity Color Orientation Spatial Frequency Motion Intensity Color Orientation Spatial Frequency Motion Saliency Map Conspicuity Maps Theory – Bottom Up Attn. Reference : Itti L, Koch C. “A Saliency-Based Search Mechanism for Overt and Covert Shifts of Visual Attention.” Vision Research, pp. 263, Vol 40(10 - 12), 2000

  8. Center Surround Mechanism Intensity Feature Maps Lateral Inhibition Intensity Conspicuity Maps

  9. Lateral Inhibition One signal vs similar signals

  10. Lateral Inhibition Purpose : Promote areas with significantly conspicuous features while suppressing those that are non-conspicuous. (After Inhibition) (Before Inhibition)

  11. Implementation • Game Logic Driven • Images too expensive • No screen space stuff • Access to game logic info

  12. Implementation – Data • Game logic data (stimulus) • Size • Attack power • Location • Health • Game logic data (goal driven) • Current selection • Visibility

  13. Computing Saliency • E.g. Saliency_Speed for object(i) • Saliency_speed(i) = (speed(i) – min_speed)/ (max_speed – min_speed) • Normalized 0 to 1 Three Normalization modes Large is important Small is imporant Closeness to mean is important

  14. Normalization Modes • Large is important • Saliency_val(i) = (val(i) – min_val) / (max_val – min_val) • Small is important • Saliency_val(i) = 1 – (val(i) – min_val) / (max_val – min_val) • Close to mean is important • Saliency_val(i) = 1 – (val(i) – avg_val) / (max_val – min_val)

  15. Normalization settings • Large is important • Size • Attack power • Targets • Speed • Small is important • Health • Close to mean is important • X, Y coordinate

  16. Lateral Inhibition • Conspicuity value = saliency_val * (max_saliency_val – min_saliency_val) • Signals with great difference between max and min get boosted

  17. Importance • Importance (i) = Sum of conspicuity_vals * weights • Weight values • Size 1.0 • Power 1.0 • X 0.5 • Y 0.5 • Health 1.0 • Targets 1.5 • Speed 1.0 • Sort list by importance

  18. Summary • Compute normalized saliency • Perform lateral inhibition • Weighted sum • Sort by importance

  19. Picking interesting object • Pick current selected • Pick current object’s target 50% of the time • Make interesting object list • From list pick top 5 randomly. Reject if it was same type as the previous object looked at.

  20. Constructing Cinematics • Local Space • Transform object space cinematic into world • Local Space without rotation frame • Use translation only • World space using reference objects • For artist driven cinematic constructed in world space • Transform to local space

  21. Local Space Cameras

  22. Flyby camera shot

  23. Circle camera shot

  24. Chase camera shot

  25. Hardpoint camera shot

  26. Frigate/Target camera shot

  27. Demo & Q&A • Thanks to • Jim Richmond for camera system • Kevin Prangley for illustrations • Petroglyph staff for support • Contact Info • Hector at petroglyphgames dot com

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