OpenGL State

GL rendering consists of geometry + state

Both are passed to graphics hardware via function calls

To draw something, the necessary state attributes (e.g. color) are set first
Then, the geometry (e.g. triangle data) is passed

State is retained until changed
State changes do not affect any geometry already drawn

State includes:

• Color
• Drawing style
• Material properties
• Light sources
• Texture
• Transformations

Example:

glColor3f(1, 1, 0)      # Set current color

glBegin(GL_TRIANGLES)

glVertex2f(0.0, 0.0)	# This triangle is yellow
glVertex2f(0.4, 0.0)
glVertex2f(0.8, 0.8)

glColor3f(1, 0, 1)      # Change current color
glVertex2f(0.0, 0.0)	# This triangle is magenta
glVertex2f(-0.4, 0.0)
glVertex2f(-0.8, -0.8)

glEnd()