The tiled texture can be well noticed even I'm using "mirror tiling" which make the terrain look unrealistic.

How do I make the terrain look realistic?

There are some ways you can improved your detail texturing.

Look here for some nice description how to avoid tiling effect.

http://udn.epicgames.com/Three/TerrainAdvancedTextures.html

In my terrain render iam using slope based methode combined with a noise map and uv mixing to give more random effect to the slope based methode.

I see that the the article is focusing on Unreal Engine, any pure D3D9 article?

You could use a level-of-detail texture which covers bigger area (less tiling) and then modulate/overlay it with a detail texture which covers smaller area (more tiling). This should give somewhat more pleasing result.

Cheers!

@kauna: Can you give idea how to do so?

I tried something like the following but couldn't get it to work:

tex1->SetLOD(10.0f);
device->SetTexture(0, tex1);
device->SetTexture(1, tex2);

d3ddev->SetTextureStageState( 0, D3DTSS_COLOROP,   D3DTOP_MODULATE );
d3ddev->SetTextureStageState( 0, D3DTSS_COLORARG1, D3DTA_TEXTURE );
d3ddev->SetTextureStageState( 0, D3DTSS_COLORARG2, D3DTA_CURRENT );
d3ddev->SetTextureStageState( 1, D3DTSS_COLOROP,   D3DTOP_MODULATE );
d3ddev->SetTextureStageState( 1, D3DTSS_COLORARG1, D3DTA_TEXTURE );
d3ddev->SetTextureStageState( 1, D3DTSS_COLORARG2, D3DTA_CURRENT );

d3d9device->SetTexture(0, detailTex);
        d3d9device->SetTexture(1, terr1Tex);

        d3d9device->SetTextureStageState( 0, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_COUNT2 );
        d3d9device->SetTextureStageState( 1, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_COUNT2 );

        D3DXMATRIX detailTrans, tex1Trans;
        D3DXMatrixScaling(&detailTrans, 16.f, 16.f, 1.f);
        D3DXMatrixScaling(&tex1Trans, 1.f, 1.f, 1.f);
        d3d9device->SetTransform( D3DTS_TEXTURE0, &detailTrans );
        d3d9device->SetTransform( D3DTS_TEXTURE1, &tex1Trans );

        d3d9device->SetTextureStageState( 0, D3DTSS_TEXCOORDINDEX, 0 );
        d3d9device->SetTextureStageState( 1, D3DTSS_TEXCOORDINDEX, 0 );

        d3d9device->SetSamplerState( 0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR );
        d3d9device->SetSamplerState( 0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR );
        d3d9device->SetSamplerState( 0, D3DSAMP_MIPFILTER, D3DTEXF_LINEAR );
        d3d9device->SetSamplerState( 1, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR );
        d3d9device->SetSamplerState( 1, D3DSAMP_MINFILTER, D3DTEXF_LINEAR );
        d3d9device->SetSamplerState( 1, D3DSAMP_MIPFILTER, D3DTEXF_LINEAR );

        d3d9device->SetTextureStageState( 0, D3DTSS_COLOROP,   D3DTOP_SELECTARG1 );
        d3d9device->SetTextureStageState( 0, D3DTSS_COLORARG1, D3DTA_TEXTURE );
        d3d9device->SetTextureStageState( 1, D3DTSS_COLOROP,   D3DTOP_MODULATE );
        d3d9device->SetTextureStageState( 1, D3DTSS_COLORARG1, D3DTA_TEXTURE );
        d3d9device->SetTextureStageState( 1, D3DTSS_COLORARG2, D3DTA_CURRENT );
        d3d9device->SetTextureStageState( 1, D3DTSS_ALPHAOP,   D3DTOP_DISABLE );
        d3d9device->SetTextureStageState( 2, D3DTSS_COLOROP,   D3DTOP_DISABLE );
        d3d9device->SetTextureStageState( 2, D3DTSS_ALPHAOP,   D3DTOP_DISABLE );

        TerrMesh->DrawSubset(0);

        d3d9device->SetTextureStageState( 0, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_DISABLE );
        d3d9device->SetTextureStageState( 1, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_DISABLE );

With detail:

Without:

@belfegor: That works well and give much better results, now, I want to apply this with my current terrain with texture splatting Pixel Shader.

How do I apply the above to my current 4 textures that I'm splatting with Pixel Shader?

This is just a multiplied with detailmap texture (with scaled texcoords). I don't know how do you want this?

Add detail texture

...
d3d9device->SetTexture(5, detailTex);
// set texcoord scale
D3DXMATRIX blendScale, texScale, detailScale;
        D3DXMatrixScaling(&blendScale, 1.f, 1.f, 1.f);
        D3DXMatrixScaling(&detailScale, 16.f, 16.f, 1.f); // you probably want to set higher scale on detail
        D3DXMatrixScaling(&texScale, 2.f, 2.f, 1.f); // then on other texs
...
d3d9device->SetTransform( D3DTS_TEXTURE5, &detailScale );

This will multiply detail with all texs

...
texld r0, t0 // scale 1
texld r1, t1 // scale 2
texld r2, t2 // scale 2
texld r3, t3 // scale 2
texld r4, t4 // scale 2
texld r5, t5 // scale 16

mul r1, r1, r0.x // multiply 1st tex with blendmap (red channel) and store result in 1st
lrp r2, r0.y, r2, r1 // lerp 2nd with 1st (blendmap green channel as factor) and store in 2nd
lrp r3, r0.z, r3, r2 // lerp 3rd with 2nd (blendmap blue channel as factor) and store in 3rd
lrp r0, r0.w, r4, r3 // lerp 4th with 3rd (blendmap alpha channel as factor) and store result in blendmap
mul r0, r5, r0 // multiply detail...

I notice few problems:

1. Something weird appear on the terrain:

[attachment=15238:weird.png]

2. The terrain appears like it's transparent, I added a sphere that intersect the terrain and I can see the bottom half of the sphere:

[attachment=15239:weird2.png]

One more thing that I want to add is 'bump map', how should update the Pixel Shader to add bump map as the 6th texture?