question

In your On Draw trigger, use the following command to undo the object's size scaling:

drawtomodelscale(current);

Also, if you want to undo the object's translation, you can use fglTranslate(). For example:

drawtomodelscale(current);
Vec3 loc = current.location;
fglTranslate(-loc.x, -loc.z, loc.y);

drawsphere(3,0,0,1,255,0,0,1,1);
drawsphere(0,3,0,1,0,255,0,1,1);
drawsphere(0,0,3,1,0,0,255,1,1);

(Note: The OpenGL coordinate space during On Draw doesn't match the FlexSim model coordinate space. The drawsphere() command already accounts for this, but the fgl() commands affect the OpenGL coordinate space directly, so Z and Y are flipped in the example fglTranslate() above. You could also fglRotate() -90 degrees around the X axis, but that would mess up the drawsphere() accounting for the different coordinate spaces.)

If you wanted to undo the object's entire transformation matrix caused by its position, rotation, and scale, then you could use fglScale(), fglTranslate(), and fglRotate():

Vec3 loc = current.location;
Vec3 rot = current.rotation;
Vec3 size = current.size;

// undo size scaling, same as drawtomodelscale(current);
fglScale(1/size.x, 1/size.z, 1/size.y);

// undo rotation
fglTranslate(size.x*0.5, size.z*0.5, size.y*0.5); // compensate for centroid rotation
fglRotate(rot.x, -1, 0, 0);
fglRotate(rot.y, 0, 0, 1);
fglRotate(rot.z, 0, -1, 0);
fglTranslate(-size.x*0.5, -size.z*0.5, -size.y*0.5);// compensate for centroid rotation

// undo position
fglTranslate(-loc.x, -loc.z, loc.y);

The "direct spatials" location [0, 0, 0] rotation [0, 0, 0] and size [1, 1, 1] is the correct size and position of an object to "draw a 1:1 sketch."

Rather than undoing the object transformations, you could alternatively just force the object's location, rotation, and size to be the values you want in an On Pre Draw trigger. That way, if something tries to change the object's position, rotation, or size, then the object simply sets it back before it draws:

current.location = Vec3(0,0,0);
current.rotation = Vec3(0,0,0);
current.size = Vec3(1,1,1);