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sakky

How to pull of some cheap FXs that look good!

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Well, I didn't know where else to put this because I wanted newbies to see this also. Also, possibly get some good comments from the other more experienced people here on GameDev. I figured that lots of the special effects see can be implemented with simple quads. Before, you people say duh, listen! Think of transitions and other things as such. Take a 2D quad and stretch it over the entire scene. You can make a fade in/out transition with adjusting it's alpha components on all 4 vertices. You could also make wipes with this. You would set the alpha component to 255 and enable alpha blending so the effect will work. Then you decrease the alpha components as time goes on making a perfect faded effect. Also, you could use this trick to make you own gamma controls because gamma controls suck! They only shade the whole screen. Where as here, you can shade what ever parts you want only by settings the alpha components and enabling alpha blending. Cool, huh? Now check this out. You can use a caustics texture of some sort and animate it with alpha blending to give a nice under water scene with out the cause of expensive shaders to render the entire scene that way. You do this by using one big quad (or many quads for a more fine effect) stretched across the screen using alpha blending. Another cool effect! Save the frames of the scene you have already rendered onto textures. They can be lower resolution but the effect won't look as good. Next, you can offset the quad(S) (or texture coordinates) and alpha blend them with different modulated diffuse colors. This will give you a really nice "I'm a drunk guy in a game!" effect. Maybe some of you have already thought of this. If not, enjoy!

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Quote:
Original post by sakky
Now check this out. You can use a caustics texture of some sort and animate it with alpha blending to give a nice under water scene with out the cause of expensive shaders to render the entire scene that way. You do this by using one big quad (or many quads for a more fine effect) stretched across the screen using alpha blending.


The standard pre-shaders way of doing caustics was one or two animated textures on the bottom of the lake/pool. You could probably find some demos of that.

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quad = quadrilatteral, i.e. a 4-sided shape.

I am using most of what you mentioned in my engine at the moment due to the lack of fancy opengl shaders on my GeForce4 and they work perfectly.

The only thing I would point out is that what you described isn't gamma control, it's brightening (yes there is a difference). Other than that, good job sharing the knowledge.

Finally, getting upset because someone hasn't replied within 5 hours is a bit daft ;)

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A Quad is a Quadilateral(4 sided) shape. You can color them , put textures on them, or any number things such as the examples by sakky. BTW I am using a texture mapped blended quad in my game to change the time of day, make it look like you are looking through a TV screen, infared filter, etc. Quads are fun [grin] !!

EDIT: Damn beaten

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Quote:
Original post by MENTAL
quad = quadrilatteral, i.e. a 4-sided shape.

I am using most of what you mentioned in my engine at the moment due to the lack of fancy opengl shaders on my GeForce4 and they work perfectly.

The only thing I would point out is that what you described isn't gamma control, it's brightening (yes there is a difference). Other than that, good job sharing the knowledge.

Finally, getting upset because someone hasn't replied within 5 hours is a bit daft ;)


1st ) it was 5 hrs and 2 minutes......hehe
2nd ) I have a GeForce4 too, cool!
3rd ) I use the quad(two triangles in a strip) with all black vertices and adjust the alpha components so that it fades in and out. With that said, if the quad was stretched over the entire scene the it would perform a cool fade in transition.
4th ) I chose gamma as a comparison. Because gamma also darkens, though I haven't seen it used for brightening (in source examples that is). But I was making a point that instead of using gamma controls that not all cards support and that only can effect the entire screen at one time, you can use my suggest to effect what ever parts yon would like.

all in all, thanks for the feed back! I'm glad someone liked what I have do say(for once).





New info! You can find more information about using effects such as these and other that use tiles in the book "Special Effects Game Programming with DirectX". This is where I got the ideas from. I'm not spamming, but I though I should at least post me reference for those interested.

As for particle engines, check out Evil Steve's particle engine...

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Maybe a bit off topic, but have you seen the Demo Effects Collection? Might give you some ideas. The site says it will build on any Unix flavored OS, but since they're done in SDL (some also in OpenGL) I don't see why you couldn't get them to work with Windows (maybe a bit of tinkering required).

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