First of all, I have to say that what I want to do here is all about Points, not objects or anything else. And my use of OpenGL is more for calculation here.
So here is my problem. I want to show some 3d points in my 2d context (winform for example or image); For this, I wrote this function: (It is in C # and uses OpenTK (OpenGL shell), but I am sure that if you know OpenGL, you can understand this regardless of your knowledge of C #)
private Vector3 GetProjectedLocation(
Vector3 pointPosition,
Vector3 cameraPosition,
Matrix4 cameraRotationMatrix)
{
float horizentalFov = MathHelper.DegreesToRadians(60.0f);
float viewRatio = (float)this.RenderSize.Width / this.RenderSize.Height;
Vector3 cameraReference = new Vector3(0, 0, -1);
Vector3 transformedReference = Vector3.Transform(cameraReference, Matrix4.Invert(cameraRotationMatrix));
Vector3 cameraLookatTarget = cameraPosition + transformedReference;
Matrix4 modelMatrix = Matrix4.Identity;
Matrix4 viewMatrix = Matrix4.LookAt(cameraPosition, cameraLookatTarget, new Vector3(0, 1, 0));
Matrix4 projectionMatrix = Matrix4.CreatePerspectiveFieldOfView(horizentalFov, viewRatio, 0.1f, 100.0f);
Matrix4 viewModelMatrix = viewMatrix * modelMatrix;
return Helper.Project(
pointPosition,
viewModelMatrix,
projectionMatrix,
new Rectangle(new Point(), this.RenderSize));
}
I also wrote another function called Project cuz. I did not find it in OpenTK:
public static Vector3 Project(Vector3 point, Matrix4 viewmodel, Matrix4 projection, Rectangle viewport)
{
Vector4 point4 = new Vector4(point, 1.0f);
Vector4 pointModel = Vector4.Transform(point4, viewmodel);
Vector4 pointProjection = Vector4.Transform(pointModel, projection);
pointProjection.W = (float)(1.0 / pointProjection.W);
pointProjection.X *= pointProjection.W;
pointProjection.Y *= pointProjection.W;
pointProjection.Z *= pointProjection.W;
return new Vector3
{
X = (float)((pointProjection.X * 0.5 + 0.5) * viewport.Width + viewport.X),
Y = (float)((pointProjection.Y * 0.5 + 0.5) * viewport.Height + viewport.Y),
Z = (float)((1.0 + pointProjection.Z) * 0.5)
};
}
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private Matrix4 CreateRotationMatrix(char axis, float radians)
{
float c = (float)Math.Cos(radians);
float s = (float)Math.Sin(radians);
if (axis == 'X')
{
return new Matrix4(1.0f, 0.0f, 0.0f, 0.0f, 0.0f, c, -s, 0.0f, 0.0f, s, c, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f);
}
if (axis == 'Y')
{
return new Matrix4(c, 0.0f, s, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, -s, 0.0f, c, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f);
}
return new Matrix4(c, -s, 0.0f, 0.0f, s, c, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f);
}
private Matrix4 MatrixFromEulerAngles(Vector3 euler, string order)
{
return CreateRotationMatrix(order[2], GetEulerAngle(order[2], euler))
* CreateRotationMatrix(order[1], GetEulerAngle(order[1], euler))
* CreateRotationMatrix(order[0], GetEulerAngle(order[0], euler));
}
private float GetEulerAngle(char angle, Vector3 euler)
{
if (angle == 'X') return euler.X;
if (angle == 'Y') return euler.Y;
return angle == 'Z' ? euler.Z : 0f;
}
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, :
"XYZ", "XZY", "YXZ", "YZX", "ZXY", "ZYX"
, .