Development > Artwork

New Feature: "Glow" textures

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arisian:
I figured I'd post this over here, rather than in the coding forum, since it's really more of an art question.

I'm planning on introducing the ability to have real-time glow/bloom effects in the battlescape, similar to what I've done for the geoscape (see screenshot).  The coding I can handle, but before that code is useful, it will require some decisions about how to use it with the artwork.

There are essentially two different ways that we can do glow.  The first is to do HDR (high-dynamic-range) rendering, in which case things will "glow" when they're brighter than the maximum brightness that can actually be displayed by your monitor (ie. if the value for the red channel is greater than 255, the "extra" red will spill over into neighboring pixels on the display).  This is how things work in the newer Halflife2 games, for example (though they do some other more complicated things as well, like adjusting the centering of the visible-dynamic-range on the fly).  New art wouldn't be required immediately, but this would wind up changing the appearance of things that were already in the game.  Given that the current textures weren't designed for HDR, this could create some issues that would require fixing textures and/or lighting to get things looking right again.

The other option is to do glow in a style that has come to be known as "Tron" style glow, since it was pioneered by the game Tron 2.0.  The idea here is that you can associate an optional extra texture with a model, much like you would a normal-map, which specifies what regions of the model should glow (along with color and intensity).  This wouldn't change the look of the game initially, but would require new art to define what should be changed and what should be left the same.

My personal preference is for the second option, at least initially (I may implement them both eventually), because it allows a much greater degree of artistic control, and I think it will fit well with the atmosphere of the game.  Having the "bright green" portions of UFOs glow, for example, seems like a natural extension of the current artistic style.  It would probably even be possible to have simple animations in which the glow-texture was varied over time, allowing things like pulsing or other fun visual effects.

The caveat, however, is that this would require new art.  Any model that didn't have an associated "glow" texture simply wouldn't glow.  This would mean that glow textures could be added slowly; the game wouldn't break because they weren't there, but new textures would have to be created before the new effects actually appeared in game.

Thoughts?

Mattn:
i would vote for hdr - but i don't know the latter technique at all. if we decide to use the latter we can add support for the mesh models very easy, and for the brushes this should go via material system.

Mattn:
oh.. the reason why i would prefer the hdr stuff is that we don't require new artwork - we are already low on artists. so we should try to do things in a way that the existing people around this project can achieve to handle it. (again, i don't know what the latter render technique would need in terms of artwork to work and look good)

H-Hour:
I vote for control over implementation rather than automated implementation (which is what I take the first method to be). I think such effects are great when used appropriately, but can be overused, like this, when every light starts to give off a ridiculous, un-natural glow. Such effects are, IMHO, best used for abstracted visuals, like the geoscape overlays. As I said, they can be used for cool effects in the battlescape, which is not supposed to have an abstracted sense of space (at least as much of one), but only in the right situations.

It's worth nothing that my opinion comes from someone who won't see the effects anyway, since I don't have a gfx card that supports that sort of stuff.

arisian:
The two techniques actually differ most in terms of what types of visual effects they allow for.  The HDR method allows for things like very brightly illuminated objects to "glow" when the lighting model calculates that the "correct" output value for a pixel is a higher value than can be displayed (ie. is greater than 1.0).  The Tron method allows for specific objects (or parts of objects) to glow regardless of lighting conditions, simply because an artist specified that they should (ie. the glow is an innate part of the object, not a result of illumination).

For the Tron-style glow, how much work would be required would depend entirely on how much stuff we wanted to have glow :)

Essentially, for any object that should have glowy-bits, you would need a new texture associated with the "standard" texture for that object.  Basically, this would work the same way that a normal-map works; just an optional extra image file with the proper suffix on its name.  That extra image would specify glow in the same way that the "standard" texture specifies diffuse reflections.

The work I did in the geoscape is actually a mish-mash of the two types; the earth itself glows using the HDR method (if you rotate the planet right, areas like ice caps or deserts will show a slight "bloom"), but the glowing borders for the nation overlay uses the Tron method, and the atmosphere uses some of each.

BTW, I'm not that familiar with the battlescape rendering system, but I don't think we should really need to add support for new meshes or brushes or anything; all we need to do is allow matterials to be associated with a glow-map the same way they currently get associated with a normal-map.

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