Re: Draw a circle in OpenGL

Barry Fishman wrote:
Elvis Nguyen <nvntung@xxxxxxxxx> writes:
Somebody test the snippets code below

(require '#:asdf)
(asdf:oos 'asdf:load-op '#:cl-glfw)
(asdf:oos 'asdf:load-op '#:cl-glfw-opengl)
(asdf:oos 'asdf:load-op '#:cl-glfw-glu)

(defconstant +DEG2RAD+ (/ 3.14159 180))

(glfw:do-window ("A Circle Example")
((gl:with-setup-projection
(glu:perspective 45 4/3 0.1 50)))
(gl:clear gl:+color-buffer-bit+)
(gl:load-identity)
(gl:translate-f 0 0 -5)

(draw-circle 100))

(defun draw-circle (radius)
(gl:with-begin gl:+line-strip+
(let ((degInRad 0))
(dotimes (i 360)
(setf degInRad (* i +DEG2RAD+))
(gl:vertex-3f (* (cos degInRad) radius) (* (sin degInRad)
radius) 0)))))

My purpose is to draw a circle using cl-glfw. The rusult is nothing. I
have tested many times.

You are trying to look at a 100 unit radius circle from 5 units away.
You need to draw a smaller circle "(draw-circle 1)", or look at it from
further away like:

(gl:translate-f 0 0 -500)

and move the perspective clipping plane further out so it doesn't
get clipped out of the picture in the process.

Or set a camera angle very close to, equaling, or exceeding 180 degrees. :)
.

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