// normal defines surface normals.
// Used in classic render mode.
func (a *Attr) normal(i int) {
if a.size != 3 {
return
}
i *= a.size
switch v := a.data.(type) {
case []int8:
gl.Normal3b(v[i], v[i+1], v[i+2])
case []int16:
gl.Normal3s(v[i], v[i+1], v[i+2])
case []int32:
gl.Normal3i(int(v[i]), int(v[i+1]), int(v[i+2]))
case []float32:
gl.Normal3f(v[i], v[i+1], v[i+2])
case []float64:
gl.Normal3d(v[i], v[i+1], v[i+2])
}
}
func gear(inner_radius, outer_radius, width float64, teeth int, tooth_depth float64) {
var i int
var r0, r1, r2 float64
var angle, da float64
var u, v, len float64
r0 = inner_radius
r1 = outer_radius - tooth_depth/2.0
r2 = outer_radius + tooth_depth/2.0
da = 2.0 * math.Pi / float64(teeth) / 4.0
gl.ShadeModel(gl.FLAT)
gl.Normal3d(0.0, 0.0, 1.0)
/* draw front face */
gl.Begin(gl.QUAD_STRIP)
for i = 0; i <= teeth; i++ {
angle = float64(i) * 2.0 * math.Pi / float64(teeth)
gl.Vertex3d(r0*math.Cos(angle), r0*math.Sin(angle), width*0.5)
gl.Vertex3d(r1*math.Cos(angle), r1*math.Sin(angle), width*0.5)
if i < teeth {
gl.Vertex3d(r0*math.Cos(angle), r0*math.Sin(angle), width*0.5)
gl.Vertex3d(r1*math.Cos(angle+3*da), r1*math.Sin(angle+3*da), width*0.5)
}
}
gl.End()
/* draw front sides of teeth */
gl.Begin(gl.QUADS)
da = 2.0 * math.Pi / float64(teeth) / 4.0
for i = 0; i < teeth; i++ {
angle = float64(i) * 2.0 * math.Pi / float64(teeth)
gl.Vertex3d(r1*math.Cos(angle), r1*math.Sin(angle), width*0.5)
gl.Vertex3d(r2*math.Cos(angle+da), r2*math.Sin(angle+da), width*0.5)
gl.Vertex3d(r2*math.Cos(angle+2*da), r2*math.Sin(angle+2*da), width*0.5)
gl.Vertex3d(r1*math.Cos(angle+3*da), r1*math.Sin(angle+3*da), width*0.5)
}
gl.End()
gl.Normal3d(0.0, 0.0, -1.0)
/* draw back face */
gl.Begin(gl.QUAD_STRIP)
for i = 0; i <= teeth; i++ {
angle = float64(i) * 2.0 * math.Pi / float64(teeth)
gl.Vertex3d(r1*math.Cos(angle), r1*math.Sin(angle), -width*0.5)
gl.Vertex3d(r0*math.Cos(angle), r0*math.Sin(angle), -width*0.5)
if i < teeth {
gl.Vertex3d(r1*math.Cos(angle+3*da), r1*math.Sin(angle+3*da), -width*0.5)
gl.Vertex3d(r0*math.Cos(angle), r0*math.Sin(angle), -width*0.5)
}
}
gl.End()
/* draw back sides of teeth */
gl.Begin(gl.QUADS)
da = 2.0 * math.Pi / float64(teeth) / 4.0
for i = 0; i < teeth; i++ {
angle = float64(i) * 2.0 * math.Pi / float64(teeth)
gl.Vertex3d(r1*math.Cos(angle+3*da), r1*math.Sin(angle+3*da), -width*0.5)
gl.Vertex3d(r2*math.Cos(angle+2*da), r2*math.Sin(angle+2*da), -width*0.5)
gl.Vertex3d(r2*math.Cos(angle+da), r2*math.Sin(angle+da), -width*0.5)
gl.Vertex3d(r1*math.Cos(angle), r1*math.Sin(angle), -width*0.5)
}
gl.End()
/* draw outward faces of teeth */
gl.Begin(gl.QUAD_STRIP)
for i = 0; i < teeth; i++ {
angle = float64(i) * 2.0 * math.Pi / float64(teeth)
gl.Vertex3d(r1*math.Cos(angle), r1*math.Sin(angle), width*0.5)
gl.Vertex3d(r1*math.Cos(angle), r1*math.Sin(angle), -width*0.5)
u = r2*math.Cos(angle+da) - r1*math.Cos(angle)
v = r2*math.Sin(angle+da) - r1*math.Sin(angle)
len = math.Sqrt(u*u + v*v)
u /= len
v /= len
gl.Normal3d(v, -u, 0.0)
gl.Vertex3d(r2*math.Cos(angle+da), r2*math.Sin(angle+da), width*0.5)
gl.Vertex3d(r2*math.Cos(angle+da), r2*math.Sin(angle+da), -width*0.5)
gl.Normal3d(math.Cos(angle), math.Sin(angle), 0.0)
gl.Vertex3d(r2*math.Cos(angle+2*da), r2*math.Sin(angle+2*da), width*0.5)
gl.Vertex3d(r2*math.Cos(angle+2*da), r2*math.Sin(angle+2*da), -width*0.5)
u = r1*math.Cos(angle+3*da) - r2*math.Cos(angle+2*da)
v = r1*math.Sin(angle+3*da) - r2*math.Sin(angle+2*da)
gl.Normal3d(v, -u, 0.0)
gl.Vertex3d(r1*math.Cos(angle+3*da), r1*math.Sin(angle+3*da), width*0.5)
gl.Vertex3d(r1*math.Cos(angle+3*da), r1*math.Sin(angle+3*da), -width*0.5)
gl.Normal3d(math.Cos(angle), math.Sin(angle), 0.0)
}
gl.Vertex3d(r1*math.Cos(0), r1*math.Sin(0), width*0.5)
gl.Vertex3d(r1*math.Cos(0), r1*math.Sin(0), -width*0.5)
gl.End()
gl.ShadeModel(gl.SMOOTH)
/* draw inside radius cylinder */
gl.Begin(gl.QUAD_STRIP)
for i = 0; i <= teeth; i++ {
angle = float64(i) * 2.0 * math.Pi / float64(teeth)
gl.Normal3d(-math.Cos(angle), -math.Sin(angle), 0.0)
gl.Vertex3d(r0*math.Cos(angle), r0*math.Sin(angle), -width*0.5)
gl.Vertex3d(r0*math.Cos(angle), r0*math.Sin(angle), width*0.5)
}
gl.End()
}