Well, i've used setBlockBounds(0.0F, 0.0F, 0.0F, 1.0F, 0.375F, 1.0F); to set my collision box, and, as 0.375 < 0.5 i expected to walk upon those blocks, but i can't. Why?

Because that's not its collision model.  It's collision model is still a full cube.

 

public AxisAlignedBB getCollisionBoundingBoxFromPool(World par1World, int par2, int par3, int par4)
{
	return AxisAlignedBB.getAABBPool().addOrModifyAABBInPool((double)par2 + this.minX, (double)par3 + this.minY, (double)par4 + this.minZ, (double)par2 + this.maxX, (double)((float)par3 + 0.125F * var5 - 0.005F), (double)par4 + this.maxZ);
}

Sure? My block extends BlockContainer that in it's turn extends Block that has next code:

 

public AxisAlignedBB getCollisionBoundingBoxFromPool(World par1World, int par2, int par3, int par4)
    {
        return AxisAlignedBB.getAABBPool().getAABB((double)par2 + this.minX, (double)par3 + this.minY, (double)par4 + this.minZ, (double)par2 + this.maxX, (double)par3 + this.maxY, (double)par4 + this.maxZ);
    }

 

And min/max x/y/z are set in setBlockBounds:

    public final void setBlockBounds(float par1, float par2, float par3, float par4, float par5, float par6)
    {
        this.minX = (double)par1;
        this.minY = (double)par2;
        this.minZ = (double)par3;
        this.maxX = (double)par4;
        this.maxY = (double)par5;
        this.maxZ = (double)par6;
    }

---

And please, use spoiler for code like that for it not to fuck the whole topic up...

Solution was just weird. This thing made the trick:

public boolean renderAsNormalBlock(){
     return false;
}