Skinning Sample

Category: Visuals

Min PC GPU: GeForce Fermi-class

Min Tegra Device: Tegra 3

@ GitHub: Skinning Sample Source Code

Description

This sample demonstrates how to render skinned meshes using both one or two bones in a vertex shader. Skinning allows organic shapes (such as humans) to deform nicely around joints as they bend. Without skinning, joints have a rigid appearance that is more similar to a mechanical joint like you would see in a robot.

APIs Used

OpenGL ES 2.0

Shared User Interface

The Graphics samples all share a common app framework and certain user interface elements, centered around the "Tweakbar" panel on the left side of the screen which lets you interactively control certain variables in each sample.

To show and hide the Tweakbar, simply click or touch the triangular button positioned in the top-left of the view.

Other controls are listed below.

Device	Input	Result
touch	1-Finger Drag	Orbit-rotate the camera
	2-Finger Drag	Move up/down/left/right
	2-Finger Pinch	Scale the view
mouse	Left-Button Drag	Orbit-rotate the camera
	Right-Button Drag	Move up/down/left/right
	Middle-Click Drag	Scale the view (up:out, down:in)
keyboard	Escape	Quit the application
	Tab	Toggle TweakBar visibility
gamepad	Start	Toggle TweakBar visibility
	Right ThumbStick	Orbit-rotate the camera
	Left ThumbStick	Move forward/backward, Slide left/right
	Left/Right Triggers	Move up/down
	A	Show TweakBar, Toggle Focused Item
	B	Close Focused UI, Hide TweakBar
	DPAD Up/Down	Move Focus to Prev/Next Item
	DPAD Left/Right	Decrease/Increase Focused Item

App-Specific Controls

This sample has the following app-specific controls:

Device	Input	Result
keyboard	M	Cycle Rendering Mode
	B	Toggle Single Bone Skinning
	[ and ]	Adjust Animation Speed Slower/Faster
gamepad	Y	Cycle Rendering Mode
	X	Toggle Single Bone Skinning
	Left/Right Shoulder Buttons	Adjust Animation Speed Slower/Faster

Technical Details

Skinning methods

Two bone skinning
- Each vertex is affected by one or two bones. The amount of the skinning effect is scaled by the weights for each bone.
One bone skinning
- Each vertex is affected by only a single bone. This doesn't lend itself to a very high quality result.

Adjustable Options

The TweakBar features the following options you can adjust:

Render Mode radio buttons
- This allows you to cycle between:
  - Rendering the diffuse color for the mesh
  - Rendering the normal for the mesh
  - Rendering a visualization of the bone weights
Single Bone Skinning checkbox
- This allows to switch between Two Bone Skinning and One Bone Skinning.
Animation Speed slider
- This allows you to speed up, slow down, and stop the animation.

Conclusion

Skinning is a good way to improve the quality of animated, organic meshes at a reasonable vertex shader cost.