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3D Terrain?! How?!

Started by alex_r Nov 2, 2004 at 4:00 PM 16 replies 3.3k views

Original Post

Nov 2, 2004 at 4:00 PM

AHOY! I have a question, how can I create a good 3D terrain system, and how can I create, or apply, the mixed texture? I like to develop a terrain like Torque... but... I don't know how begin, there any tutorial or article about it?

ehmdjii

Nov 2, 2004 at 5:01 PM

lots of articles about terrain:

http://www.gamedev.net/reference/list.asp?categoryid=45#88

alex_r

Nov 2, 2004 at 11:53 PM

...sorry... I forgot these articles :-/

The topic update:
I just need to know how create the mixed texture...
How can I do this?

skow

Nov 2, 2004 at 11:57 PM

I think you need to slow down. Read up on multi-texturing and blending.

ehmdjii

Nov 3, 2004 at 5:17 AM

here is a tutorial for you:

http://www.gametutorials.com/Tutorials/opengl/OpenGL_Pg4.htm

celestialVoid

Nov 3, 2004 at 7:06 AM

Quote:
Original post by alex_r
I just need to know how create the mixed texture...
How can I do this?

There are more methods to do it. For example,Texture Splatting.
More: Terrain texturing

You could also use a shader. Here is a brief example I wrote (Cg shader):

////////////////////// Vertex Program //////////////////////struct VP_OUTstr{	float4 position  : POSITION;	float2 texcoord0 : TEXCOORD0;	float2 texcoord1 : TEXCOORD1;	float2 texcoord2 : TEXCOORD2; };VP_OUTstr vp_main (uniform float4x4   modelviewmatrix, 		float4 pos : POSITION,		float2 texcoord0 : TEXCOORD0,		float2 texcoord1 : TEXCOORD1,		float2 texcross	: TEXCOORD2){	VP_OUTstr OUT;	OUT.texcoord0 = texcoord0;	OUT.texcoord1 = texcoord1;	OUT.texcoord2 = texcross;		OUT.position = mul (modelviewmatrix, pos);		return OUT;}//////////////////////// Fragment Program ////////////////////////struct FP_OUTstr{	float4 color : COLOR;};FP_OUTstr fp_main (uniform sampler2D tex0,		uniform sampler2D tex1,		float2 texcoord0 : TEXCOORD0,		float2 texcoord1 : TEXCOORD1,		float2 texcross  : TEXCOORD2){	FP_OUTstr OUT;		float4 color0 = tex2D (tex0, texcoord0);	float4 color1 = tex2D (tex1, texcoord1);	OUT.color = lerp (color0, color1, texcross);	return OUT;}

This shader works per-vertex, but it shouldn't be to hard to extend it to per-fragment level using control maps (you have an image where different color means different texture - you then texture the terrain based on this image).
Above code demonstrates that with two textures, which are then interpolated.
'tex0' and 'tex1' are textures to be interpolated.
'texcoord0', 'texcoord1' are coordinates of these two textures.
'texcross' is an array which holds how much these two texture will be interpolated, and where on the surface.
For example, if you had 6x4 vertices surface, you would apply one texture to the left side of it like this:

float texture_cross [] = { 1.0f,1.0f, 1.0f,1.0f, 0.0f,0.0f,
0.0f,0.0f, 0.0f,0.0f, 0.0f,0.0f,

1.0f,1.0f, 1.0f,1.0f, 0.0f,0.0f, 0.0f,0.0f, 0.0f,0.0f, 0.0f,0.0f,

1.0f,1.0f, 1.0f,1.0f, 0.0f,0.0f, 0.0f,0.0f, 0.0f,0.0f, 0.0f,0.0f,

1.0f,1.0f, 1.0f,1.0f, 0.0f,0.0f, 0.0f,0.0f, 0.0f,0.0f, 0.0f,0.0f,
};

Each pair of elements in this arrays represents one vertex. You can now think of the surface like:
1 1 0 0 0 0
1 1 0 0 0 0
1 1 0 0 0 0
1 1 0 0 0 0

where 1 is the first texture, and 0 is the second. In the end, you get something like this:

If you need more details, just ask.

alex_r

Nov 3, 2004 at 7:16 AM

Thanks Wingman, it is easy to do... :D

I have a idea how can I develop my terrain system...

first is a height map, to develop the texture, I think it:

1 = Grass texture
2 = Dust texture
3 = Rock texture
4 = Water texture

in terrain file I place the texture info like this:

411111141
112222442
122114411
123214111
111111111

with this info I create a big texture for the terrain with the mix...
Like this, the first water texture (1,1), I mix with the grass texture (1,2; 2,2; 2,1)...

Is like a layer picture, the first layer is the height value, the second is the texture, 3 is the models ( tree, plants... )...

Thanks everyone for the help :D

alex_r

Nov 3, 2004 at 8:47 PM

AHOY AGAIN!

Here is my first terrain editor test... This is just a height map, now I'm testing how can I "paint" the texture and modele the terrain.

http://sites.vortexentertainment.com/alex_r/terraintest.jpg

Thx...

Ademan555

Nov 4, 2004 at 2:09 AM

Well... out of curiosity, is anyone in here using brute force terrain? if not, what LOD algo are you using?

thanks
-Dan

alex_r

Nov 4, 2004 at 3:16 AM

Quote:
Original post by Ademan555
Well... out of curiosity, is anyone in here using brute force terrain? if not, what LOD algo are you using?

thanks
-Dan

There no lod and frustum yet... Now I just working in the paint system...

Now the terrain have dynamic shadow, with the Matthew Strahan shadow system (http://www.gamedev.net/reference/articles/article2125.asp)
Here is the final result with shadow, PLEASE!!! IGNORE THE TEXTURE :D hehehehehe

http://sites.vortexentertainment.com/alex_r/terrainshadow.jpg

To create the mountain I get the distance from the center to the border from the circle (red circle), every point inside this circle can be changed... :)
I think I can use the same to create the textures. I got one cool sample from Delphi3D (http://www.delphi3d.net/articles/viewarticle.php?article=terraintex.htm), I think to use the same system too. I just need to understand to "port" to C++ :-/

ade-the-heat

Nov 4, 2004 at 5:54 AM

I understand how you get the vertices in the shadow - but what do you color the vertex by ? eg do you color the vertex black if in the shadow and then modulate it with the grass texture color ?

cheers

alex_r

Nov 4, 2004 at 6:08 AM

I set the vertex color, like it: glColor3f(0.5f, 0.5f, 0.5f);

PsyVision

Nov 4, 2004 at 6:18 AM

Ademan,

I use a quadtree for my terrain and then frustum cull the quads and then occlusion cull from the list of ones in the frustum, each quad is rendered using VBO's.

This is the result:

http://www.psyvision.co.uk/graphics.JPG
http://www.psyvision.co.uk/screen.jpg

alex_r

Nov 4, 2004 at 12:57 PM

Very good PsyVision!!!

I need to read more about quads and VBOs, you know any good article about it?

...I don't know anything about it... but, pelase, don't tell it to anyone... :p hehehe

zedzeek

Nov 4, 2004 at 1:24 PM

Quote:
Original post by Ademan555
Well... out of curiosity, is anyone in here using brute force terrain? if not, what LOD algo are you using?

thanks
-Dan

in the method in the screenshot below, im going (1 dimensional explanation)

4 patches of say 8meter's wide == LOD 0
4 patches of say 16meter's wide == LOD 1
4 patches of say 32meter's wide == LOD 2
etc
i draw everything with quad's but on the borders between the patches, i split the lower res quad into 3 triangles (so i dont get cracks)

alex_r

Nov 4, 2004 at 1:52 PM

Quote:
Original post by Anonymous Poster
alex_r,

How do you draw those circles on the terrain (the red and yellow circles). I'm assuming this is a cursor for your to use as a painting tool on your terrain, how do you do that?

Thanks!

void MapEditorDrawCursor(){	int X = 0;	float x = 0;	float z = 0;	V_Graphic.v_Begin_Poly(VG_LINE_STRIP);	V_Graphic.v_SetColor3(1.0f, 0.0f, 0.0f);	for( X = 0; X <= 360; X+= 45 )	{		x = float(16 * cos(deg2rad(0+X)));		z = float(16 * sin(deg2rad(0+X)));		V_Graphic.v_DrawVertex( x+MouseCursorX, Height(x+MouseCursorX, z+MouseCursorY ), z+MouseCursorY );	}	V_Graphic.v_SetColor3(1.0f, 1.0f, 0.0f);	for( X = 0; X <= 360; X+= 45 )	{		x = float(32 * cos(deg2rad(0+X)));		z = float(32 * sin(deg2rad(0+X)));		V_Graphic.v_DrawVertex( x+MouseCursorX, Height(x+MouseCursorX, z+MouseCursorY ), z+MouseCursorY );	}	V_Graphic.v_End_Poly();}

zedzeek, how you calcule the distance?

alex_r

Nov 4, 2004 at 9:01 PM

zedzeek, is like this:
Dist = sqrt((double)(val[0]*val[0] + val[1]*val[1] + val[2]*val[2]));

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