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DarkBASIC Professional Discussion / Draw only part of an object.

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Green Gandalf
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Posted: 26th Aug 2013 15:15
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Here's a simple demo showing what can happen when an animated object walks through a clipping plane. The shader demonstrates what Chris Tate and I have been saying about the use of clip() - there are no weird gaps or uninitialized parts of the scene, i.e. the background plane is textured as you would expect.

The shader uses two passes: exposed unclipped back facing pixels are coloured red, front facing unclipped pixels are textured normally.



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chafari
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Posted: 26th Aug 2013 16:13
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@TheComet & Green Gandalf

Until now, I didn't realize what a great shader you made guys ...Thanks for sharing

I'm not a grumpy grandpa
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TheComet
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Posted: 26th Aug 2013 16:15 Edited at: 26th Aug 2013 16:21
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Quote: "Here's a simple demo showing what can happen when an animated object walks through a clipping plane. The shader demonstrates what Chris Tate and I have been saying about the use of clip() - there are no weird gaps or uninitialized parts of the scene, i.e. the background plane is textured as you would expect.

The shader uses two passes: exposed unclipped back facing pixels are coloured red, front facing unclipped pixels are textured normally."


Could you possibly post a few screen shots of it in action? I'm at work right now and am itching to see it, but can't for another 6 hours or so.

[EDIT] Thanks chafari!

TheComet

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Green Gandalf
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Posted: 26th Aug 2013 16:30 Edited at: 26th Aug 2013 16:31
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Here's one as she starts to walk through the invisible clipping plane. Her nose, right forearm, chest and left leg have been clipped.



Moral: don't walk through sheets of glass.



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TheComet
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Posted: 26th Aug 2013 16:50
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Aah, so you're using the insides of the object to serve as the edge colour! That's quite ingenious, nicely done. I have one tiny proposal, would it make more sense to use no culling at all instead of clockwise culling in the first pass?



TheComet

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Green Gandalf
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Posted: 26th Aug 2013 17:33 Edited at: 26th Aug 2013 17:42
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Quote: " I have one tiny proposal, would it make more sense to use no culling at all instead of clockwise culling in the first pass?"


No - because then the front and back polys would both be drawn and it would probably be a matter of luck which would be drawn first. In fact it probably makes sense to draw the front facing polys first since then only the exposed back facing polys would be drawn. At the moment all back facing polys are drawn when they pass the Z depth test even if the second pass subsequently draws over them. Results should be the same though but there might be a tiny performance boost.

Edit Just noticed:

Quote: "Location: I`m under ur bridge eating ur CATS"


Noooooooo!

Afterthought You're right about there being an issue with "open" objects. This can happen if you're using a sphere to do the culling as the reverse side might be culled too so you'll get a gap where you can see the background. But turning off culling won't be the solution.

Afterthought2 Ah! Just realised it might be the solution but you'd have to fiddle with the z tests or something to ensure the second pass doesn't fail the z test. I'll think about it. Good point!



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TheComet
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Posted: 26th Aug 2013 18:00 Edited at: 26th Aug 2013 18:04
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I think disabling writing to the depth buffer will do this:



Or was it ZENABLE? One of those.

[EDIT]
Quote: "Noooooooo!"


...WHO'S WALKING OVER MY KONG® Denim Tunnel, growled the troll-cat with a deep voice...

Arguably one of the best children stories of all time.

TheComet

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Southside Games
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Posted: 26th Aug 2013 18:27 Edited at: 26th Aug 2013 18:40
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hey. I'll compile the new sonar blast shader.

No, the edges don't need to be colored.

Edit:

Hey the update looks good. and yes I typed in the wrong thing, though to be fair I copied the code on how to use.

Also I found if I make the line really thick I get the effect I want-ish.

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TheComet
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Posted: 26th Aug 2013 18:51
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Quote: "Also I found if I make the line really thick I get the effect I want-ish."


I'm guessing you want the "normal" texture to be drawn on one side of the sphere, and another, new texture to be drawn on the inside of the sphere?

TheComet

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Southside Games
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Posted: 26th Aug 2013 19:10 Edited at: 26th Aug 2013 19:11
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No. I want only the part inside the radius to be drawn. But really I just needed to show a path that would otherwise not be seen.
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TheComet
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Posted: 26th Aug 2013 19:18
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Ooh, you want to combine the two shaders? Well that's pretty straight forward, but I'm going to let GG do that (because I'm at work).

TheComet

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Posted: 26th Aug 2013 19:30 Edited at: 26th Aug 2013 19:31
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well work bro

edit:

mmm... well maybe combining them could work, you know? the Mario shader would only draw the part the player is standing on, and the sonar blast one would do the outline.
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Southside Games
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Posted: 28th Aug 2013 01:44
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Hey Comet. Is it possible to have multiple pings in your sonar effect? Or would I need to make more copies of the effect and apply them to copies of the object that would be pinged?
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TheComet
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Posted: 28th Aug 2013 01:59
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Sure, two questions:

1) How many do you need at maximum?
2) Do they all originate from the same location, or different locations?

TheComet

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Southside Games
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Posted: 28th Aug 2013 02:01 Edited at: 28th Aug 2013 03:53
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4 max. And at different locations.

edit:

thanks bro. this is really cool of you.
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