Designing Games with Game Maker - YoYo Games

indicated amount.
d3d_transform_add_translation(xt,yt,zt) Adds a translation over
the indicated vector.
d3d_transform_add_scaling(xs,ys,zs) Adds a scaling with the
indicated amounts.
d3d_transform_add_rotation_x(angle) Adds a rotation around the x-
axis with the indicated amount.
d3d_transform_add_rotation_y(angle) Adds a rotation around the y-
axis with the indicated amount.
d3d_transform_add_rotation_z(angle) Adds a rotation around the z-
axis with the indicated amount.
d3d_transform_add_rotation_axis(xa,ya,za,angle) Adds a rotation
around the axis indicated by the vector with the indicated amount.
Realize that rotation and scaling are with respect to the origin of the world, not with respect to
the object that is to be drawn. If the object is not at the origin it will also move to a different
place, which is not what we want. So to e.g. rotate an object over its own x-axis, we must first
translate it to the origin, next rotate it, and finally translate it back to its position. This is what
the functions to add transformations are for.
The following examples might explain this better. Assume we have a sprite spr that we want
to draw at position (100,100,10). We can use the following code to do this
{
d3d_transform_set_translation(100,100,10);
draw_sprite(spr,0,0,0);
d3d_transform_set_identity();
}
Note that because we use a translation we should now draw the sprite at position (0,0). (This
assumes the current instance has a depth of 0! If you are not sure, first set the depth.) If we
would use this in our first person shooter we would not see the sprite. The reason is that it is
still parallel to the xy-plane. We want to rotate it over 90 degrees along the x-axis (or y-axis).
So we need to add a rotation. Remember the order: we must first rotate the sprite and then
translate it. So we can use the following code.