Triangle

[kugimasa]

GOAL

The cursor draws the triangle. The triangle gets bigger(or smaller).

• [x] Input from cursor using GLUT

• [x] Draw triangle

• [x] Match coordinate system

• [x] Draw triangle in polar coordinate system

• [x] Move triangle according to cursor position

• [x] Change triangle size

• [x] Change triangle color

• [x] Draw triangle when cursor is not moving

• [x] Add motion blur

[kugimasa]

Input from cursor using GLUT

glutPassiveMotionFunc() : Get the cursor position in the window (x, y) when nothing is pressed

Commit here

[kugimasa]

Draw Triangle

The origin of Cursor Coordinate System and Display Coordinate System is different

Commit here

[kugimasa]

Match Coordinate System

displayX =   2.0 * (cursorX / w) - 1.0
displayY = - 2.0 * (cursorY / y) + 1.0

Commit here

[kugimasa]

Draw triangle in polar coordinate system

x = cos(theta)
y = sin(theta)

The 3 vertexes' position

• theta = PI/2

Commit [here]()

• theta = 7PI/6
• theta = 11PI/6

Commit [here]()

[kugimasa]

Move triangle according to cursor position

Commit here

[kugimasa]

Change triangle size

Commit here

[kugimasa]

Change triangle color

Commit here

[kugimasa]

Draw triangle when cursor is not moving (and Refactor)

glutIdleFunc()

Commit here

[kugimasa]

Add motion blur

glEnable(GL_BLEND) and glBlendFunc(src, dst)

Commit here