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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 (Order Independent) Transparency

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Hello guys,

I started implementing transparency in my engine, and I got stuck on the usualy problem, I think, even thought I can't find very much helpful stuff on this.

I use a classic blendmode for transparent objects, and order them by the distance from the cam before drawing. This works fine if they are just a bunch of objects on behind another, but as soon as I rotate them or a model contains multiple polygons which have to been blended over oneanother, it becomes problematic.

For the rotationpart, I suppose I need a way to check the point of the object closest to the cam, and order them by this point rather than by just their position.

But I can't see someone preordering the triangles inside a mesh to get which transparent one needs to get drawn first.

As a solution, I have read about Order Independent Transparency, which is only for dx11, but that would be fine with me. I can't seem to pick up a good tutorial on this, so I may aswell ask you for one.

Or do you have another way of fixing those two problems?

 

Thanks so much!

-gnomgrol

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I had some help earlier on a similar issue, if you search for the topic "Rendering Intersecting Premultiplied Transparent Planes" and look at the Billboard example in the Microsoft XNA samples site they show how two passes can be used to prevent intersecting planes from creating weird depth effects.

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There's the 'OIT11' sample in the DirectX SDK. It's an expensive technique, though. You can often get away by using simple additive blending.

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Additive blending is the only blending that can be drawn without drawing back to front, yes, for everything else I always implemented a simple binary tree that receives all the triangles being sent to the renderer, inserting them into the tree based on their distance, and then when its time to draw them to the screen I just walk the tree drawing from back to front, deconstructing the tree as the triangles are rendered. This entails building a new tree each frame, but it could be set up to only build a new tree once things have moved around enough to require a new tree being built. Also, for large triangles that could be intersecting eachother this won't work properly, but it works well enough for most cases. If you have a lot of triangles in your scene, its better to precompute something like a BSP tree for the static geometry, as it wouldn't be very efficient to rebuild a distance binary tree every frame (or even every couple of frames) for tens-of-thousands of triangles.

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Hi!

 

What you ended up using is called „alpha test“ and is not truly a solution to the blending of many transparent objects, though it is a common hack to avoid the problem.

Whenever you really need to approach true order-independent transparency, there are a number of methods:

  • Depth peeling [Everitt 01, Bavoil & Myers 08] (Requires to know the number of layers, but was used quite often in research papers. Also works on Dx9.)
  • Concurrent linked list construction [Yang et al. 10, Yakiimo 10]-> do not look into the DxSDK sample (OIT11). Last time I looked, it was poorly implemented (didn’t use shared memory at all).  Check the version of Yakiimo. He implemented it faster, even with multi-sampling. This technique grew more useful by the recent advances of the graphics hardware. Requires Dx11.
  • Stochastic transparency [Enderton et al. 10] (also rather a research thingy. It can handle an arbitrary number of layers, but consumes much performance to get it frame-to-frame coherent). Needs Dx 10.1 if I recall correctly, as it works on the coverage mask.
  • The list goes on... stencil routing etc... (Look into the related work of the papers I linked, if you want to learn more.)

AFAIK, true order-independent transparency was yet too expensive for games. (If someone knows a game that used OIT, please let me know!) It is easier to work around it or just sort the transparent objects by depth. (Of course, this doesn’t work in all cases, but you can tell your artist to circumvent the ugly cases.)
I’m creating technical demos and prototypes, so I can afford to use the concurrent linked list construction.

 

Best regards!
 

PS: Links don't seem to work at the moment, so I post the URLs.

Everitt 01: http://gamedevs.org/uploads/interactive-order-independent-transparency.pdf

Baviol & Myers 08: http://developer.download.nvidia.com/SDK/10/opengl/src/dual_depth_peeling/doc/DualDepthPeeling.pdf

Yang et al. 10: http://onlinelibrary.wiley.com/doi/10.1111/j.1467-8659.2010.01725.x/abstract

Yakiimo 10: http://www.yakiimo3d.com/2010/07/19/dx11-order-independent-transparency/

Enderton et al. 10: http://www.enderton.org/eric/pub/StochasticTransparency_I3D2010.pdf

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