Qexpo Tutorial Day 4

<-Day 3

Day 5->

The story so far: we’ve skinmapped this much of the weaponmodel. We’ve basically got the body of the thing done, and on a slightly less complex model like the Q1 Shotgun, we might be just wrapping up right now. However, this one has lots of fiddly extras, which will be good practice, so let’s get cracking!

t4i01

We’ll start with one of the canisters, pick the one standing vertically.

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t4s01From the shape of it, I’d hope you’d anticipate we’re gonna do a cylindrical mapping on this bit, and that’s exactly right. Apply the UVW map, do a cylindrical map with cap, aligned to X, and press the fit button. Also apply an unwrap UVW and go to edit. You’ll spot we have the same problem as with the nozzle yesterday: everything is piled up on the same section of skin, so we’d better untangle them.

t4s02The procedure is the same as yesterday, using the red plus button to select whole parts. You’ll notice that again the capped surfaces are fragmented in this editor, so you can’t select all of one of the end faces just by pressing the red plus button. You could do what we did last time, select the faces in the main editor, apply an Unwrap to just the selected faces, then go and weld them up, hut we don’t really need to, since all these part can he mapped to the same piece of skin here. Just seperate out the pieces as shown here.

t4s03We can also save space on the skin by mirroring the bottom third of the cylinder onto the top third. Select all those vertices, flip them vertically with the tool indicated. Then move it on top of the other section. We could have moved it straight there without flipping it but it makes more sense this way. so the outside edges match up.

So we’ve skinned one canister, but we don’t want to go through all that again twice more. and wouldn’t it save space if all of the canisters used the same area of skin? Yeah, of course it would. So the plan is to clone the skinned cylinder and copy it into the place of the unskinned ones, then delete the unskinned ones. Hold down shift, then move the skinned cylinder about to create a clone. Select copy from the box that pops up and click ok. Move and rotate the clone into place and finally delete the original.

Next up is the trigger guard:

t4i03

This doesn’t need to he skinned especially carefully as it’s a small detail. So select the left and right side faces, and apply a planar map aligned to X to both of them(so they both get mapped to the same bit of skin). You may find the “ignore backfacing” checkbox in the selection panel helpful for selecting the second side of the trigger. Scale, tweak and collapse the modifiers. then select all the other faces, and do a planar map from front to back. It’s not really worth tweaking the distortion here, so just scale and move to the side with the Unwrap UVW editor.

Okay, moving on, the shoulder rest:

t4i04

The above also shows the face you should select first. Apply a planar map to these faces. and then tweak them to get rid of the bits of distortion on the ends, it shouldn’t take much. Then select the other 4 sides and apply a cylindrical map to these. It’s not much of a cylinder, but this means the whole thing is skinmapped as one continuous part. Where the skin won’t get distorted it’s good to keep pieces as continuous as possible for two reasons. One is that the places on a model where the skinmap isn’t continuous are often obvious and ugly, unless it;s very carefully skinned. These are called seams, and it’s good practice to try and put them where they can’t be seen if you can; for instance on the insides of legs on a humanoid model. The larger the angle between faces, the easier it is to get away with a seam, so it’s not that important here, but still. The other reason is that too many pieces increase the number of vertices that are generated in the final Quake model, and there’s a limit of 100 per model.

Apply a cylindrical map aligned to X with no cap, then press the fit button. Oh dear.

t4s04That hasn’t turned out all that great, it’s very uneven and distorted. Look to the length parameter, indicated in the screenshot.

t4s05Keep decreasing the length until the circle of the cylinder looks like the oval pictured here, just touching the edge of the shoulder rest. The proportion of skin given to the side is way off compared to the top, but the side faces are no longer distored with respect to each other. Go in with the UVW Unwrap editor and correct the ratio of the sides to the top, and tweak out those last bits of distortion manually. It’s easiest to scale the whole thing vertically so the sides aren’t distorted. then edit the top and bottom.

t4s06While we’re at it, it’s probably worth mirroring one of the sides onto the other. This is just like yesterday, when we moved a triangle from one side of the nozzle to the other. We’re simply moving more triangles. and mirroring them first this time. Here’s the step by step. 1: select all the vertices along the line we are cutting along. 2:Click on “break vertices”. 3: Select all the other vertices in the piece we are going to move. 4: click on expand selection to select the other vertices we want to move but are hidden under vertices we don’t want to select. 5: Click on weld selected to make it one piece to move.

Then just mirror horizontally, move into position, select all the vertices and weld selected again. The shoulder rest is now done, collapse the modifiers and get ready for the hardest part, the pipes.

t4i05

As they stand, there’s really no easy way to skin these things. The pipes basically started as cylinders so it might have been easier to skin them when they were cylinder shaped. There’s the benefit of hindsight, but what can we do now? Well, either we can make a cylinder, skin it, and then try to recreate the pipes from scratch, or we can do something more subtle and flexible.

t4s07Clone this length of pipe, go to the modifier tab and go to vertex level selection(the first button on the selection tab). The plan is to edit this pipe back into a rough approximation of a cylinder’. Select all the vertices of one “loop” of the pipe and without worrying about anything else for now, just rotate them so that they are in a
vertical circle facing the front of the gun. The screenshot shows the first two loops already rotated, and the third loop selected. with the original pipe for comparison.

t4s08Once all the loops face the same way, it’s time to translate them. Just move them each in turn until they line up in all the screens. It doesn’t have to be perfect so long as it’s fairly cylindrical. The screenshot shows three of them lined up. The spacing doesn’t have to be even either, that gets sorted out later.

t4s09One final check now that the bits are aligned is to look in the front window and make sure that none of the loops are “twisted”. Each of the long lines running down the cylinder should be basically straight, rotate the loops if this isn’t the case. Fit a cylindrical map in the X direction around this clone. and open up the UV editor. You should see something like this, it’s wobbly but recognisable. Using the scale tools, select each row and column in turn and squash it until it is straight. The selected column of vertices has already been done as a demonstration.

t4s10Collapse the modifiers, then make two clones of the newly skinmapped straight pipe, for future use. Unhide everything, and then apply a “morpher” modifier to one of the straight pipes. 1: Click on the “Pick Object from Scene” button. and then click on one of the curved pipes. Go down to the entry in the Channel List. and change the percentage in the box from 0 to 100. The skinned pipe suddenly becomes the correct shape. Collapse the modifiers again. Do the same with the two cloned, skinned pipes, giving them the morph targets of the other two pipes. Then, like we did with the cylinders, move the skinned versions into place and delete the originals. You’ll notice that the squares on the pipe aren’t evenly sized. and aren’t even off by the same amount on each pipe. All of which means you’re gonna have to mess around with Unwrap UVW” for each pipe for a while. Keep everything in a neat grid when you edit it, just move the lines about. The skin is a little distorted on the curves, but it works quite well in practice.

The reason I’d keep the skin this way touches on another thing to consider when skinmapping. and how it relates to skinning. When I skin this model, I see the pipes as being ribbed metal. so along the whole length it has straight lines wrapping around the pipe. making the individual rings of the texture. Now, the crucial thing is that straight lines look best on a skin if they actually run in a straight line vertically or horizontally, it avoids jaggedness. This is why the pipe is skinmapped in such a way that every horizontal corresponds to a loop around the pipe. Two things to take away from this digression: The specific point is that if there are important straight lines in your design, try to put them on the horizontal or vertical. The more general remark is that the skinmap and the skin are deeply connected. Thought put into the skinmap will make the skin that much easier to make, and thinking about the skin ahead of time will help you make decisions about the skinmap. It’s all very well reflecting the torso of a player left to right on the skinmap to save space, but it does mean you can’t put an asymetrical design on it, which is very limiting.

Okay, enough philosophy stuff – back to something practical. We need to put all of the objects into a single object so we can edit the skinmaps together and export it. Select one of the pieces, go to the modifier tab, collapse its modifiers and click the “attach list” button, over on the right hand panel under the heading “edit geometry”. Select everything that comes up in the dialogue box and press attach. Then apply an Unwrap UWV modifier. and click edit.

t4s11This is what I see, your view may vary depending on how you skinned things, resized them. or placed them. I admit I’ve been doing something without telling you all this time. Each time I’ve finished a piece I’ve moved them to what I hoped would be their own bit of space on the UV grid. And mostly it’s worked, thanks to the benefit of foresight, although there are a few bits still overlapping. You already know how to sort out overlapping pieces from previous parts of the tutorial, so separate everything else out into it’s own bit of space with the help of the red plus button. If you really can’t see through a tangle of polygons, collapse the modifier and go to object selection(the one to the right of face selection). Select just one object, hide the rest, then use the UV editor to move it out of the jumble. Collapse everything and repeat until you can manage it.

t4s12This is what I’ve got now everything is separated out. I’ve actually put all three pipes on top of one another, so they can share the same skin. The next thing to do is look around the mapped model, and see if the squares are the same scale on each piece. In general, you want about the same pixel density on each piece of your model, although it’s a also a judgement call. You don’t want to devote much of the skin to the tiny trigger guard, but if you want to put some writing on the canisters you might want to give them more skin to accommodate it.

One tip I’ve picked up is to give proportionally more skin to the head of a human/monster than any other part. People will tend to look at the head more than anything else, just by instinct, so you may as well put more detail into it.

Now we get to what I regard as the fun bit. You have all the bits of the puzzle, and you now have to pack them as tightly as possible without overlapping them. Don’t do stupid things now just to make them fit better, like rotating the pipes at 45 degrees after all that talk about lining them up with the horizontal. On a more organic model you’d have many more options with the rotations. A good rule of thumb is to start with the largest pieces, but you’ve got to experiment to get the best usage.

Another thing is to remember what size of space you are packing them into. Because of the way graphics cards store textures, you really should make the dimensions of your skins powers of 2, like 256×256 or 512×128. I know that none of the original Quake models do, but that’s a bad thing. GLQuake just stretches the skins to the nearest power of two, which is kinda ugly. More recent engines deal with things better by padding the skin out with blank pixels, but that’s just wasting memory you could use to put more detail into your model. So fit things into the square. When I finished up, I got this:

t4s14
Make sure that the vertices don’t go outside the box, or it’ll crash QME. So, it’s now time to export things. Do exactly what we did in the 2nd tutorial, right up to replacing the previous version of v_rock.mdl. Unlike the sphere you shouldn’t need to scale this weapon, but displace it up by 24 units up at the QME stage. Load up Quake and you should see this:

t4s15

Phew! I’m gonna go make an actual skin for this model, it’s not turned out that bad, and I’m sure someone can find a use for it. Next time we’ll look at skeletons and skeletal animation.

Margin note 5
It took 7 years for me to make that actual skin, but the fusion cannon can now be downloaded and enjoyed.

<-Day 3

Day 5->

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