Dragon Age II DX11 TechnologyAndreas Papathanasis

BioWare

• Sequel to the successful RPG

Dragon Age: Origins• Focus on combat, magic,

cinematics• Rebooted Art Style, focus on

Graphics technology• Out next week on PC / Xbox 360 / PS3

Our pitch for DX11 technologyWe discussed within our project tiered options for taking advantage of next generation PC GPUs:

– Tier 0: DX9 with very high quality shaders– Tier 1: Basic DX11 integration

• No compute or tessellation shaders• Takes advantage of shader models 4 and 5

– Tier 2: Typical DX11 integration• Compute and tessellation shaders fully supported

– Tier 3: Advanced DX11 integration • Multithreading• Requires significant refactoring of the higher level engine

Why DirectX 11?• Opportunities to integrate well documented, impactful visual

features using SM4/SM5, new shader stages• Guaranteed feature set (no cap bits)• Great way for programming and art teams to prepare for the next

generation• Powerful, evolving debugging tools

GPU PerfStudio 2 – Shader Debugging on DX10/DX11

Why DirectX 11?

• Reliable backwards compatibility with older hardware

• Customers have the hardware and expect games that use it

Steam hardware survey

DirectX 11 features overview• Dynamic lighting • Tessellation• Diffusion Depth of Field• Contact hardening soft shadows

Dynamic Lighting

Dynamic Lighting

Dynamic Lighting• Based on the popular light pre-pass method

– http://www.wolfgang-engel.info/blogs/?p=26

• Extra pass to render scene normals • Render all dynamic light spheres to a light buffer• Allows for hundreds of lights• Minimal engineering effort to integrate on

DX11: – Multiple render targets work with MSAA– Guaranteed render target format support– Small per-draw overhead on the CPU

• Makes a lot of sense for a spell-rich game like Dragon Age II

Light buffer

Tessellation• Big research focus for the team

– Great potential for taking geometric detail to the next level

– Lends itself to LOD naturally, without affecting CPU or complicating the engine codebase

Tessellation challenges• Piecewise level construction

– can cause gaps between adjacent objects when normals don’t match at the edges– would require content to be redone for DX11– fell back to parallax mapping techniques for displaced look– ongoing research topic for our next projects

• Some content (i.e. characters) is already tessellated at desired density for non DX11 platforms

• On Dragon Age II we used tessellation for terrain silhouette smoothing (using PN triangles algorithm)

Tessellation on terrainWithout tessellation With tessellation

Tessellation performance• VERY easy to kill performance with excessive tessellation• Performance improvements that made a difference in our engine (sorted in

order of the performance win we got):– Only tessellate objects close enough to the camera– LOD in the hull shader

• View frustum culling (important for high polygon objects that span a large area, like terrain)

• Distance adaptive tessellation factor

– Only tessellate objects that will end up being visible (occlusion culling even more relevant if you’re rendering lots of tessellated objects)

Diffusion Depth of Field• Custom multi-pass Diffusion DOF solver

– Technique will be described by Holger Gruen later today, and appear in Game Engine Gems 2

– Much higher quality than our DX9 DOF solution, almost as efficient

Diffusion Depth of FieldDX9 DOF

Diffusion DOF

Diffusion Depth of Field DX9 DOF

Diffusion Depth of FieldDiffusion DOF

Contact hardening shadows

Contact hardening shadows• High quality shadow filter• Accelerated by GatherRed/GatherCmpRed

Shader Model 5 instructions• Shader source code in the DirectX SDK• Trivial to integrate, great visual quality

improvement for directional shadows

Contact hardening shadowsOld PCF filter

Non uniform contact hardening filter

References• Light pre-pass

http://www.wolfgang-engel.info/blogs/?p=26

• PN triangle implementation –June 2010 DirectX SDK, PNTriangles11 sample

• Diffusion DOF solverGame Engine Gems 2 (http://www.gameenginegems.net/)

• Contact hardening soft shadows–June 2010 DirectX SDK, ContactHardeningShadows11 sample

Conclusion• API and market is mature• Lots of algorithms available that can enhance

your particular style of game• Initial investment in DX11 integration should

pay off quickly• Hardware vendors can help you

Q & A

andreas@bioware.com

DirectX 11 DirectX 9