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    • By stale
      I'm continuing to learn more about terrain rendering, and so far I've managed to load in a heightmap and render it as a tessellated wireframe (following Frank Luna's DX11 book). However, I'm getting some really weird behavior where a large section of the wireframe is being rendered with a yellow color, even though my pixel shader is hard coded to output white. 

      The parts of the mesh that are discolored changes as well, as pictured below (mesh is being clipped by far plane).

      Here is my pixel shader. As mentioned, I simply hard code it to output white:
      float PS(DOUT pin) : SV_Target { return float4(1.0f, 1.0f, 1.0f, 1.0f); } I'm completely lost on what could be causing this, so any help in the right direction would be greatly appreciated. If I can help by providing more information please let me know.
    • By evelyn4you
      Hello,
      i try to implement voxel cone tracing in my game engine.
      I have read many publications about this, but some crucial portions are still not clear to me.
      At first step i try to emplement the easiest "poor mans" method
      a.  my test scene "Sponza Atrium" is voxelized completetly in a static voxel grid 128^3 ( structured buffer contains albedo)
      b. i dont care about "conservative rasterization" and dont use any sparse voxel access structure
      c. every voxel does have the same color for every side ( top, bottom, front .. )
      d.  one directional light injects light to the voxels ( another stuctured buffer )
      I will try to say what i think is correct ( please correct me )
      GI lighting a given vertecie  in a ideal method
      A.  we would shoot many ( e.g. 1000 ) rays in the half hemisphere which is oriented according to the normal of that vertecie
      B.  we would take into account every occluder ( which is very much work load) and sample the color from the hit point.
      C. according to the angle between ray and the vertecie normal we would weigth ( cosin ) the color and sum up all samples and devide by the count of rays
      Voxel GI lighting
      In priciple we want to do the same thing with our voxel structure.
      Even if we would know where the correct hit points of the vertecie are we would have the task to calculate the weighted sum of many voxels.
      Saving time for weighted summing up of colors of each voxel
      To save the time for weighted summing up of colors of each voxel we build bricks or clusters.
      Every 8 neigbour voxels make a "cluster voxel" of level 1, ( this is done recursively for many levels ).
      The color of a side of a "cluster voxel" is the average of the colors of the four containing voxels sides with the same orientation.

      After having done this we can sample the far away parts just by sampling the coresponding "cluster voxel with the coresponding level" and get the summed up color.
      Actually this process is done be mip mapping a texture that contains the colors of the voxels which places the color of the neighbouring voxels also near by in the texture.
      Cone tracing, howto ??
      Here my understanding is confus ?? How is the voxel structure efficiently traced.
      I simply cannot understand how the occlusion problem is fastly solved so that we know which single voxel or "cluster voxel" of which level we have to sample.
      Supposed,  i am in a dark room that is filled with many boxes of different kind of sizes an i have a pocket lamp e.g. with a pyramid formed light cone
      - i would see some single voxels near or far
      - i would also see many different kind of boxes "clustered voxels" of different sizes which are partly occluded
      How do i make a weighted sum of this ligting area ??
      e.g. if i want to sample a "clustered voxel level 4" i have to take into account how much per cent of the area of this "clustered voxel" is occluded.
      Please be patient with me, i really try to understand but maybe i need some more explanation than others
      best regards evelyn
       
       
    • By Endemoniada

      Hi guys, when I do picking followed by ray-plane intersection the results are all wrong. I am pretty sure my ray-plane intersection is correct so I'll just show the picking part. Please take a look:
       
      // get projection_matrix DirectX::XMFLOAT4X4 mat; DirectX::XMStoreFloat4x4(&mat, projection_matrix); float2 v; v.x = (((2.0f * (float)mouse_x) / (float)screen_width) - 1.0f) / mat._11; v.y = -(((2.0f * (float)mouse_y) / (float)screen_height) - 1.0f) / mat._22; // get inverse of view_matrix DirectX::XMMATRIX inv_view = DirectX::XMMatrixInverse(nullptr, view_matrix); DirectX::XMStoreFloat4x4(&mat, inv_view); // create ray origin (camera position) float3 ray_origin; ray_origin.x = mat._41; ray_origin.y = mat._42; ray_origin.z = mat._43; // create ray direction float3 ray_dir; ray_dir.x = v.x * mat._11 + v.y * mat._21 + mat._31; ray_dir.y = v.x * mat._12 + v.y * mat._22 + mat._32; ray_dir.z = v.x * mat._13 + v.y * mat._23 + mat._33;  
      That should give me a ray origin and direction in world space but when I do the ray-plane intersection the results are all wrong.
      If I click on the bottom half of the screen ray_dir.z becomes negative (more so as I click lower). I don't understand how that can be, shouldn't it always be pointing down the z-axis ?
      I had this working in the past but I can't find my old code
      Please help. Thank you.
    • By turanszkij
      Hi,
      I finally managed to get the DX11 emulating Vulkan device working but everything is flipped vertically now because Vulkan has a different clipping space. What are the best practices out there to keep these implementation consistent? I tried using a vertically flipped viewport, and while it works on Nvidia 1050, the Vulkan debug layer is throwing error messages that this is not supported in the spec so it might not work on others. There is also the possibility to flip the clip scpace position Y coordinate before writing out with vertex shader, but that requires changing and recompiling every shader. I could also bake it into the camera projection matrices, though I want to avoid that because then I need to track down for the whole engine where I upload matrices... Any chance of an easy extension or something? If not, I will probably go with changing the vertex shaders.
    • By evelyn4you
      Hello,
      in my game engine i want to implement my own bone weight painting tool, so to say a virtual brush painting tool for a mesh.
      I have already implemented my own "dual quaternion skinning" animation system with "morphs" (=blend shapes)  and "bone driven"  "corrective morphs" (= morph is dependent from a bending or twisting bone)
      But now i have no idea which is the best method to implement a brush painting system.
      Just some proposals
      a.  i would build a kind of additional "vertecie structure", that can help me to find the surrounding (neighbours) vertecie indexes from a given "central vertecie" index
      b.  the structure should also give information about the distance from the neighbour vertecsies to the given "central vertecie" index
      c.  calculate the strength of the adding color to the "central vertecie" an the neighbour vertecies by a formula with linear or quadratic distance fall off
      d.  the central vertecie would be detected as that vertecie that is hit by a orthogonal projection from my cursor (=brush) in world space an the mesh
            but my problem is that there could be several  vertecies that can be hit simultaniously. e.g. i want to paint the inward side of the left leg. the right leg will also be hit.
      I think the given problem is quite typical an there are standard approaches that i dont know.
      Any help or tutorial are welcome
      P.S. I am working with SharpDX, DirectX11
        
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DX11 DirectCompute and Multi-GPU

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Hi,

 

I am working actually on my compute shader based fluid simulation and I thought to power it up by testing two GTX980 in SLI. Finally I noticed that there is no benefit because he's using only one GPU. However I think it could be possible by using two DX11 devices bound to booth adapters. In that case the first could run the rest of my application (deferred lighting stuff and others) and the second one haves enough power for my phyisics. So my questions are: Is that possible? I think I would need some kind of device independend buffers to share the result of the physics.

 

Does everyone have some expirience here?

 

Thx,

Thomas

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IIRC DX11 won't allow you to share resources between GPU's you'd need DX12 to do that.  So you'd need to copy data to a 'bounce buffer' in system memory instead of directly from one GPU to the other.  Also I seem to recall someone saying SLI needs to be programmed for explicitly... but don't quote me on that.  But anyway DX12 has something called explicit multi-GPU which is what you're looking for.

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mhh this is really frustrating, because I am bound to slimdx and there is no dx12. But the strange thing is, that its already possible for PhysX to move this to the second card and I don't think that PhysX is moving all the data back to CPU.

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IIRC Physx uses CUDA so maybe there are Nvidia proprietary libraries that will let you do it.  If I were you I would look into amd and nvidia proprietary libraries and there multi-gpu programming stuff before you give up.  However not that many people have multiple gpu's so is it really that big a deal?  I wish I could help you more but my knowledge is with dx12 multi-gpu.  Heres a link in case you want to take a look.  https://msdn.microsoft.com/en-us/library/windows/desktop/dn933253(v=vs.85).aspx

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In the case of an SLI setup, there is no way to individually target the specific GPUs in D3D11. Things like PhysX are implemented using driver extensions which allow things like that.

If you just have a system with two GPUs in it that are not linked, then they show up through DXGI as two separate adapters, and you can create two devices on them. However, there is no real way to synchronize them.

 

If you wanted to have one of them do physics and feed it back to the CPU, and the other do rendering and feed it to the display, that would work just fine. But having the physics fed directly to the other device in a queued manner (i.e. record physics, record graphics, execute physics, execute graphics) isn't really possible, you'd have to have the CPU step in (i.e. record physics, execute physics, record graphics, execute graphics).

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It's either SLI or multi-device. One excludes the other.

 

My experience with DirectCompute is dated and possibly obsolete at this point. Nonetheless, I still remember how painful it was. FXC took bloody hours to compile my kernels as opposed to OpenCL which mangled them in less than a minute and produced 30% higher perf as result.

 

Historically, multi-device implies some low-perf path in the driver. Caution advised. Anyhow,

 

Hi,

 

I am working actually on my compute shader based fluid simulation and I thought to power it up by testing two GTX980 in SLI. Finally I noticed that there is no benefit because he's using only one GPU. 

How did you determine this? The main point of SLI is that it's supposed to be transparent to the application. The promise is that they sync the devices for you (bleh).

Indeed, performance SLI requires explicit support as there are a couple hundreds issues to deal with and ways to shoot yourself in both perf feet.

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