NVPR Text Wheel

Category: Visuals

Min PC GPU: Fermi-based (GTX 4xx)

Min Tegra Device: Tegra K1

Description

This sample demonstrates using the NV_path_rendering OpenGL extension to draw text arranged like spokes in a wheel, with a slight 3D projection applied to the rendering.

APIs Used

NV_path_rendering
EXT_direct_state_access

Shared User Interface

The OpenGL 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	2-Finger Drag	Translate the view
	2-Finger Pinch	Scale the view
mouse	Left-Click Drag	Translate the view
	Right-Click Drag	Scale the view (up:out, down:in)
keyboard	Escape	Quit the application
	Tab	Toggle Tweakbar visibility
gamepad	Start	Toggle Tweakbar visibility

App-Specific Controls

This sample has the following app-specific controls:

Device	Input	Result
keyboard	space	Toggle Animation
	F	Toggle Path Fill
	S	Toggle Path Stroke
gamepad	Y	Toggle Animation
	Left Shoulder Button	Toggle Path Fill
	Right Shoulder Button	Toggle Path Stroke

Technical Details

This sample demonstrates NV_path_rendering drawing spinning text with a slight projection applied to the text arranged in a spinning wheel. The shading of the text uses a smooth color gradient generated with glPathColorGenNV.

The glyphs for the text on the spinning wheel are created with the glPathGlyphRangeNVcommand.

The text spacing with kerning is determined with the glGetPathSpacingNVquery.

The instanced path APIs are used to efficiently draw the filled and stroked text: