In this post we’ll be doing some heavy math to calculate the distance between BF and EN. And to learn a little more gl, we’ll be displaying the data, like so:
Note the nice circular formation of the cubes – this is a stable “merry-go-round” configuration in which the friends chase each other in a circle while keeping their enemies at least one cube distant. See my last post for the starting positions and relationships that create this very nice pattern.
The first part of this patch is to make the stack of cubes in the upper left corner. We do this by dumping just the color information from the points table, and incrementing the y position of the cube placement using the index.
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Once the cubes are drawn once, we can leave them; the renderer will happily render them each frame.
Now we need to calculate the distance from each cube to its EN. To do this, we use the 3d equivalent of Pythagorean theorem (a2 + b2 = c2), which is:
x2 + y2 + z2 = d2
where x, y, and z here refer to the distance between the cube and its EN, and d is the resultant distance. So if we think of the cube as being at x1, y1, z1 and its EN as being at x2, y2, z2
then we can more accurately use the formula:
To carry this out, we’ll take the result of the vector subtraction we used earlier in creating the “normalized vectors” and feed it into:
expr sqrt(($f1*$f1) + ($f2*$f2) + ($f3*$f3))
And store the results in a new coll called “dist2enemy”
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Lastly we need to dynamically add the text next to each cube, indicating the distance from that cube to its EN.
Here we need to make modifications to the rendering section of our previous patch:
Our metro needs to be replaced with a qmetro because we will be drawing the text in between the erasure and re-rendering of the GL context. Because we must execute all eight draw events between the erase and the render, Max needs to know to wait for these events before pushing ahead, which is the purpose of qmetro. You can think of it as a variable-speed metro that slows down to make sure that every event in its path takes place before it sends another “bang.”
We’ll add this send betw_e_b so we can get a “bang” in the moment right after the context is erased and right before it is re-rendered.
In this patch we use that bang to dump the dist2enemy table, using the index to set the y location of the text (assuring that the correct value will appear next to each cube), and drawing the text using a jit.gl.text2d object with @automatic set to 0 (so multiple drawing between renders in enabled):
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