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Decals – When are you going to grow up?
Bobby Miller
January 5, 2009 4:59 PM ET in Gaming
Everything has moved on up. Why not decals?
Have you ever seen a war zone post-battle? It’s not a clean picture. Walls are rendered to the likeness of Swiss cheese with bullet holes, terrain is blackened and charred by scorch marks from open flames, and in most cases blood runs red where bullets have met flesh. This is a picture of total destruction, the reality of warfare. So why, in an age where video games attempt to render virtual battlegrounds in a completely photorealistic fashion, the details of ‘battle scars’ fail so greatly to reach that bar?
All gamers are familiar with decals. You fire a pistol at a wall and a bullet hole appears. Spin the tires on a 400 horsepower Corvette and tire marks trail your path. Cast a lightning spell into a room and scorch marks betray its presence. It’s not new technology, it’s been around for a long time in gaming. But graphics technology has far surpassed the still primitive decal in terms of realism and presentation.
Years ago I sat down to play our newly purchased NASCAR ‘98 with my brother, Andy. I remember vividly how excited we were that when you spun out, there were tire marks. This was revolutionary! The illusion of realism was shattered for us rather quickly however, the tire marks would disappear after a very short amount of time. Andy and I discussed how incredible it was going to be years down the road once technology progressed so far that these marks would never disappear. In our minds there would soon be a time when bullet holes and tire marks would stay indefinitely and look just as detailed as they do in reality.
Decals were very limited back then. In the case of NASCAR ‘98 and Goldeneye64, two games that implemented 2 very different types of decals, the overlays would disappear after a matter of seconds and had no variety in their appearance.
Big progression came by the name of Payne. Max Payne in 2001 was a step in the right direction for decal technology. Not only did decals stay for a very long time, there was a ton of variance in them dependent upon the type of material hit. Wood splintered, metal dented, and paper shredded. Observing the aftermath of a shootout in Max Payne told a story of powerful weapons and complete destruction. This was a step closer to the future I had expected 4 years earlier.
F.E.A.R., released in 2005, brought a new kind of technological leap for decals – parallax mapping. When you fire your weapons at a wall, the result is pixel shader use to give a 2D texture the illusion of depth. The decal changes dynamically based on light sources in the room and the player’s perspective in relation to the damage. The result is damaged surfaces that look as if they’ve lost a physical portion of its mass. This savage and brutal aftermath showed us what we could expect with next gen decals.
This has hardly become the standard in games today however. Many games seem to push technology in every department but decals, triple A titles not withstanding. I find this to be strange. Emergent gameplay and immersion are two of the biggest buzzword objectives in video games today, yet disappearing decals, (or the complete lack thereof) shatter that illusion very quickly.
No example has made this more clear to me recently as Far Cry 2 has. The game is beautiful and dances on the line of photorealism. It’s easy to be completely sucked into FarCry 2’s massive and gorgeous world. Firefights are intense and brutal as plants break apart and fire propagates realistically. When the fighting is over there’s not much that tells the story of the battle that just took place. The weak bullet hole decals that happen from gunshots typically fade away before the fight is over.
Decals: When will you grow up? Watch hi-res to see what we mean.
This is not an uncommon trend in modern games. Despite computer hardware having progressed to incredible levels, decals still seem to be in a primitive state with many games. Bioshock and Mass Effect are two modern shooters that have weak decals with short lifespans. Grid, a racing game with outstanding visuals has tire marks that disappear after a lap or two. Shouldn’t decal life be increasing along with the increase in computer memory and processing power? It seems as if rather than pushing this aspect of computer graphics, most developers have been taking a step backwards.
One of the best steps to take would be to follow in F.E.A.R.’s footsteps. Parallax maps leave convincing and impressive results and the small expense of GPU usage. There are few computers out there that can’t handle advanced pixel shaders. Beyond Parallax maps would be moving to the use of displacement mapping for decals.
Displacement mapping is an advanced graphics technique that actually alters the geometric positions of points on a mesh. What this means is that if the technique was used for bullet impacts, the surface effected would be physically altered at the point of impact. A hole would be created that fully reacts to viewer position, light and shadow, and perspective appropriately. This is an intensive technique due to the additional geometry created, so it’s implementation into real-time graphics is still rather emergent.
The use of either Parallax or displacement maps as decals would significantly increase the realism of decals at the cost of GPU processing power. With the power behind modern GPU’s, there’s no reason to not use some of it to rendering more detailed decals. If developers would embrace these advanced techniques we would benefit with much more convincing game worlds.
To boost variety in decals, developers could turn to procedural generation. This method would create a new decal texture in real time as it’s needed based simply on mathematical calculations. The possible creations with this method are infinite. The user would never see the same decal twice. Due to the unpredictable nature of ballistics and damage, this would raise the bar in realism.
There have been far too many advancement in real-time computer graphics to leave the simple decal at such an archaic state. We shouldn’t be excited when I still see tire marks after lap three or bullet impacts remain after a firefight. Those are hurdles the industry should have cleared long ago. When I compare explosion craters lasting for hours in Command and Conquer back in 1995 to a single bullet hole lasting a minute in Far Cry 2 today, I see a terrible lack of progress.
No matter how developers approach decals, they absolutely should make an effort to focus on it just as much as they do in other areas of graphics. If anything, decals quickly fading out should be put to rest for good. There are impressive new technologies that are just asking to be used for more realistic decal effects. The illusion of reality is made present by the details, and I feel like decals are one crucial detail developers are missing.
Like the racing games that adore them, decal use seems to be a technology that’s spinning its tires. Perhaps it’s time to grip the pavement and move forward.
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