• 12
• 12
• 9
• 10
• 13
• ### Similar Content

• By elect
Hi,
ok, so, we are having problems with our current mirror reflection implementation.
At the moment we are doing it very simple, so for the i-th frame, we calculate the reflection vectors given the viewPoint and some predefined points on the mirror surface (position and normal).
Then, using the least squared algorithm, we find the point that has the minimum distance from all these reflections vectors. This is going to be our virtual viewPoint (with the right orientation).
After that, we render offscreen to a texture by setting the OpenGL camera on the virtual viewPoint.
And finally we use the rendered texture on the mirror surface.
So far this has always been fine, but now we are having some more strong constraints on accuracy.
What are our best options given that:
- we have a dynamic scene, the mirror and parts of the scene can change continuously from frame to frame
- we have about 3k points (with normals) per mirror, calculated offline using some cad program (such as Catia)
- all the mirror are always perfectly spherical (with different radius vertically and horizontally) and they are always convex
- a scene can have up to 10 mirror
- it should be fast enough also for vr (Htc Vive) on fastest gpus (only desktops)

Looking around, some papers talk about calculating some caustic surface derivation offline, but I don't know if this suits my case
Also, another paper, used some acceleration structures to detect the intersection between the reflection vectors and the scene, and then adjust the corresponding texture coordinate. This looks the most accurate but also very heavy from a computational point of view.

Other than that, I couldn't find anything updated/exhaustive around, can you help me?

• Hello all,
I am currently working on a game engine for use with my game development that I would like to be as flexible as possible.  As such the exact requirements for how things should work can't be nailed down to a specific implementation and I am looking for, at least now, a default good average case scenario design.
Here is what I have implemented:
Deferred rendering using OpenGL Arbitrary number of lights and shadow mapping Each rendered object, as defined by a set of geometry, textures, animation data, and a model matrix is rendered with its own draw call Skeletal animations implemented on the GPU.   Model matrix transformation implemented on the GPU Frustum and octree culling for optimization Here are my questions and concerns:
Doing the skeletal animation on the GPU, currently, requires doing the skinning for each object multiple times per frame: once for the initial geometry rendering and once for the shadow map rendering for each light for which it is not culled.  This seems very inefficient.  Is there a way to do skeletal animation on the GPU only once across these render calls? Without doing the model matrix transformation on the CPU, I fail to see how I can easily batch objects with the same textures and shaders in a single draw call without passing a ton of matrix data to the GPU (an array of model matrices then an index for each vertex into that array for transformation purposes?) If I do the matrix transformations on the CPU, It seems I can't really do the skinning on the GPU as the pre-transformed vertexes will wreck havoc with the calculations, so this seems not viable unless I am missing something Overall it seems like simplest solution is to just do all of the vertex manipulation on the CPU and pass the pre-transformed data to the GPU, using vertex shaders that do basically nothing.  This doesn't seem the most efficient use of the graphics hardware, but could potentially reduce the number of draw calls needed.

Really, I am looking for some advice on how to proceed with this, how something like this is typically handled.  Are the multiple draw calls and skinning calculations not a huge deal?  I would LIKE to save as much of the CPU's time per frame so it can be tasked with other things, as to keep CPU resources open to the implementation of the engine.  However, that becomes a moot point if the GPU becomes a bottleneck.

• Hello!
I would like to introduce Diligent Engine, a project that I've been recently working on. Diligent Engine is a light-weight cross-platform abstraction layer between the application and the platform-specific graphics API. Its main goal is to take advantages of the next-generation APIs such as Direct3D12 and Vulkan, but at the same time provide support for older platforms via Direct3D11, OpenGL and OpenGLES. Diligent Engine exposes common front-end for all supported platforms and provides interoperability with underlying native API. Shader source code converter allows shaders authored in HLSL to be translated to GLSL and used on all platforms. Diligent Engine supports integration with Unity and is designed to be used as a graphics subsystem in a standalone game engine, Unity native plugin or any other 3D application. It is distributed under Apache 2.0 license and is free to use. Full source code is available for download on GitHub.
Features:
True cross-platform Exact same client code for all supported platforms and rendering backends No #if defined(_WIN32) ... #elif defined(LINUX) ... #elif defined(ANDROID) ... No #if defined(D3D11) ... #elif defined(D3D12) ... #elif defined(OPENGL) ... Exact same HLSL shaders run on all platforms and all backends Modular design Components are clearly separated logically and physically and can be used as needed Only take what you need for your project (do not want to keep samples and tutorials in your codebase? Simply remove Samples submodule. Only need core functionality? Use only Core submodule) No 15000 lines-of-code files Clear object-based interface No global states Key graphics features: Automatic shader resource binding designed to leverage the next-generation rendering APIs Multithreaded command buffer generation 50,000 draw calls at 300 fps with D3D12 backend Descriptor, memory and resource state management Modern c++ features to make code fast and reliable The following platforms and low-level APIs are currently supported:
Windows Desktop: Direct3D11, Direct3D12, OpenGL Universal Windows: Direct3D11, Direct3D12 Linux: OpenGL Android: OpenGLES MacOS: OpenGL iOS: OpenGLES API Basics
Initialization
The engine can perform initialization of the API or attach to already existing D3D11/D3D12 device or OpenGL/GLES context. For instance, the following code shows how the engine can be initialized in D3D12 mode:
#include "RenderDeviceFactoryD3D12.h" using namespace Diligent; // ...  GetEngineFactoryD3D12Type GetEngineFactoryD3D12 = nullptr; // Load the dll and import GetEngineFactoryD3D12() function LoadGraphicsEngineD3D12(GetEngineFactoryD3D12); auto *pFactoryD3D11 = GetEngineFactoryD3D12(); EngineD3D12Attribs EngD3D12Attribs; EngD3D12Attribs.CPUDescriptorHeapAllocationSize[0] = 1024; EngD3D12Attribs.CPUDescriptorHeapAllocationSize[1] = 32; EngD3D12Attribs.CPUDescriptorHeapAllocationSize[2] = 16; EngD3D12Attribs.CPUDescriptorHeapAllocationSize[3] = 16; EngD3D12Attribs.NumCommandsToFlushCmdList = 64; RefCntAutoPtr<IRenderDevice> pRenderDevice; RefCntAutoPtr<IDeviceContext> pImmediateContext; SwapChainDesc SwapChainDesc; RefCntAutoPtr<ISwapChain> pSwapChain; pFactoryD3D11->CreateDeviceAndContextsD3D12( EngD3D12Attribs, &pRenderDevice, &pImmediateContext, 0 ); pFactoryD3D11->CreateSwapChainD3D12( pRenderDevice, pImmediateContext, SwapChainDesc, hWnd, &pSwapChain ); Creating Resources
Device resources are created by the render device. The two main resource types are buffers, which represent linear memory, and textures, which use memory layouts optimized for fast filtering. To create a buffer, you need to populate BufferDesc structure and call IRenderDevice::CreateBuffer(). The following code creates a uniform (constant) buffer:
BufferDesc BuffDesc; BufferDesc.Name = "Uniform buffer"; BuffDesc.BindFlags = BIND_UNIFORM_BUFFER; BuffDesc.Usage = USAGE_DYNAMIC; BuffDesc.uiSizeInBytes = sizeof(ShaderConstants); BuffDesc.CPUAccessFlags = CPU_ACCESS_WRITE; m_pDevice->CreateBuffer( BuffDesc, BufferData(), &m_pConstantBuffer ); Similar, to create a texture, populate TextureDesc structure and call IRenderDevice::CreateTexture() as in the following example:
TextureDesc TexDesc; TexDesc.Name = "My texture 2D"; TexDesc.Type = TEXTURE_TYPE_2D; TexDesc.Width = 1024; TexDesc.Height = 1024; TexDesc.Format = TEX_FORMAT_RGBA8_UNORM; TexDesc.Usage = USAGE_DEFAULT; TexDesc.BindFlags = BIND_SHADER_RESOURCE | BIND_RENDER_TARGET | BIND_UNORDERED_ACCESS; TexDesc.Name = "Sample 2D Texture"; m_pRenderDevice->CreateTexture( TexDesc, TextureData(), &m_pTestTex ); Initializing Pipeline State
Diligent Engine follows Direct3D12 style to configure the graphics/compute pipeline. One big Pipelines State Object (PSO) encompasses all required states (all shader stages, input layout description, depth stencil, rasterizer and blend state descriptions etc.)
To create a shader, populate ShaderCreationAttribs structure. An important member is ShaderCreationAttribs::SourceLanguage. The following are valid values for this member:
SHADER_SOURCE_LANGUAGE_DEFAULT  - The shader source format matches the underlying graphics API: HLSL for D3D11 or D3D12 mode, and GLSL for OpenGL and OpenGLES modes. SHADER_SOURCE_LANGUAGE_HLSL  - The shader source is in HLSL. For OpenGL and OpenGLES modes, the source code will be converted to GLSL. See shader converter for details. SHADER_SOURCE_LANGUAGE_GLSL  - The shader source is in GLSL. There is currently no GLSL to HLSL converter. To allow grouping of resources based on the frequency of expected change, Diligent Engine introduces classification of shader variables:
Static variables (SHADER_VARIABLE_TYPE_STATIC) are variables that are expected to be set only once. They may not be changed once a resource is bound to the variable. Such variables are intended to hold global constants such as camera attributes or global light attributes constant buffers. Mutable variables (SHADER_VARIABLE_TYPE_MUTABLE) define resources that are expected to change on a per-material frequency. Examples may include diffuse textures, normal maps etc. Dynamic variables (SHADER_VARIABLE_TYPE_DYNAMIC) are expected to change frequently and randomly. This post describes the resource binding model in Diligent Engine.
The following is an example of shader initialization:
To create a pipeline state object, define instance of PipelineStateDesc structure. The structure defines the pipeline specifics such as if the pipeline is a compute pipeline, number and format of render targets as well as depth-stencil format:
// This is a graphics pipeline PSODesc.IsComputePipeline = false; PSODesc.GraphicsPipeline.NumRenderTargets = 1; PSODesc.GraphicsPipeline.RTVFormats[0] = TEX_FORMAT_RGBA8_UNORM_SRGB; PSODesc.GraphicsPipeline.DSVFormat = TEX_FORMAT_D32_FLOAT; The structure also defines depth-stencil, rasterizer, blend state, input layout and other parameters. For instance, rasterizer state can be defined as in the code snippet below:
// Init rasterizer state RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc; RasterizerDesc.FillMode = FILL_MODE_SOLID; RasterizerDesc.CullMode = CULL_MODE_NONE; RasterizerDesc.FrontCounterClockwise = True; RasterizerDesc.ScissorEnable = True; //RSDesc.MultisampleEnable = false; // do not allow msaa (fonts would be degraded) RasterizerDesc.AntialiasedLineEnable = False; When all fields are populated, call IRenderDevice::CreatePipelineState() to create the PSO:
Shader resource binding in Diligent Engine is based on grouping variables in 3 different groups (static, mutable and dynamic). Static variables are variables that are expected to be set only once. They may not be changed once a resource is bound to the variable. Such variables are intended to hold global constants such as camera attributes or global light attributes constant buffers. They are bound directly to the shader object:

m_pPSO->CreateShaderResourceBinding(&m_pSRB); Dynamic and mutable resources are then bound through SRB object:
m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "tex2DDiffuse")->Set(pDiffuseTexSRV); m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB); The difference between mutable and dynamic resources is that mutable ones can only be set once for every instance of a shader resource binding. Dynamic resources can be set multiple times. It is important to properly set the variable type as this may affect performance. Static variables are generally most efficient, followed by mutable. Dynamic variables are most expensive from performance point of view. This post explains shader resource binding in more details.
Setting the Pipeline State and Invoking Draw Command
Before any draw command can be invoked, all required vertex and index buffers as well as the pipeline state should be bound to the device context:
// Clear render target const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); // Set vertex and index buffers IBuffer *buffer[] = {m_pVertexBuffer}; Uint32 offsets[] = {0}; Uint32 strides[] = {sizeof(MyVertex)}; m_pContext->SetVertexBuffers(0, 1, buffer, strides, offsets, SET_VERTEX_BUFFERS_FLAG_RESET); m_pContext->SetIndexBuffer(m_pIndexBuffer, 0); m_pContext->SetPipelineState(m_pPSO); Also, all shader resources must be committed to the device context:
m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); When all required states and resources are bound, IDeviceContext::Draw() can be used to execute draw command or IDeviceContext::DispatchCompute() can be used to execute compute command. Note that for a draw command, graphics pipeline must be bound, and for dispatch command, compute pipeline must be bound. Draw() takes DrawAttribs structure as an argument. The structure members define all attributes required to perform the command (primitive topology, number of vertices or indices, if draw call is indexed or not, if draw call is instanced or not, if draw call is indirect or not, etc.). For example:
DrawAttribs attrs; attrs.IsIndexed = true; attrs.IndexType = VT_UINT16; attrs.NumIndices = 36; attrs.Topology = PRIMITIVE_TOPOLOGY_TRIANGLE_LIST; pContext->Draw(attrs); Tutorials and Samples
The GitHub repository contains a number of tutorials and sample applications that demonstrate the API usage.

AntTweakBar sample demonstrates how to use AntTweakBar library to create simple user interface.

Atmospheric scattering sample is a more advanced example. It demonstrates how Diligent Engine can be used to implement various rendering tasks: loading textures from files, using complex shaders, rendering to textures, using compute shaders and unordered access views, etc.

The repository includes Asteroids performance benchmark based on this demo developed by Intel. It renders 50,000 unique textured asteroids and lets compare performance of D3D11 and D3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

Integration with Unity
Diligent Engine supports integration with Unity through Unity low-level native plugin interface. The engine relies on Native API Interoperability to attach to the graphics API initialized by Unity. After Diligent Engine device and context are created, they can be used us usual to create resources and issue rendering commands. GhostCubePlugin shows an example how Diligent Engine can be used to render a ghost cube only visible as a reflection in a mirror.

• By Yxjmir
I'm trying to load data from a .gltf file into a struct to use to load a .bin file. I don't think there is a problem with how the vertex positions are loaded, but with the indices. This is what I get when drawing with glDrawArrays(GL_LINES, ...):

Also, using glDrawElements gives a similar result. Since it looks like its drawing triangles using the wrong vertices for each face, I'm assuming it needs an index buffer/element buffer. (I'm not sure why there is a line going through part of it, it doesn't look like it belongs to a side, re-exported it without texture coordinates checked, and its not there)
I'm using jsoncpp to load the GLTF file, its format is based on JSON. Here is the gltf struct I'm using, and how I parse the file:
glBindVertexArray(g_pGame->m_VAO);
glDrawElements(GL_LINES, g_pGame->m_indices.size(), GL_UNSIGNED_BYTE, (void*)0); // Only shows with GL_UNSIGNED_BYTE
glDrawArrays(GL_LINES, 0, g_pGame->m_vertexCount);
So, I'm asking what type should I use for the indices? it doesn't seem to be unsigned short, which is what I selected with the Khronos Group Exporter for blender. Also, am I reading part or all of the .bin file wrong?
Test.gltf
Test.bin

• That means how do I use base DirectX or OpenGL api's to make a physics based destruction simulation?
Will it be just smart rendering or something else is required?

# OpenGL Need help getting started with direct volume rendering.

This topic is 2509 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

I'm trying to learn voxel rendering with gpu raycasting in XNA. I'm not making a minecraft clone but I want the terrain to have a similar cuboid appearance, just on a larger scale. I've seen software renderers on youtube that can render 1024^3 volumes, so I should be able to do just as good or better with the gpu right? My goal is a volume of 1024x1024x64. Ideally it would twice those dimensions. I'd like to have the voxels textured with diffuse lighting and possibly ambient occlusion.

Anything I search for leads me to acceleration structures and other advanced concepts. I can't find anything on how to just do the basics. The only thing I've been able to actually understand and implement is this, which uses a weird method that doen't seem normal to me. Primarily it only works when the camera is outside of the volume.

My experience with graphics programming isn't much beyond basic polygon phong shading and shadow maps. Is jumping straight into direct volume rendering too big of a leap? It seems that much of the material I find assumes a good understanding of raytracing. I can understand the concepts of the 3DDDA traversal and sparse voxel octrees, but I don't know how to actually put them in place.

Based on the example in the link, I've got raycasting and traversing though the volume and sampling a color from a 3d texture. It uses a weird light accumulation thing to make it look all transparent and medical-like. I'm trying to get started from that but I'm not getting any further.

My first question is whether I should stick with XNA. I know it's not the best choice for this, but is it a terrible choice? It's what I'm most familiar with and I would like to publish to XBLIG. I've never really made anything with OpenGl but that would be the alternative, mostly to go multiplatform.

Second, how do you get the per-pixel raycasting going? The example draws a polygon cube to get to the pixel shader. I would think using a quad and putting it in front of the camera would be better. I'm sure there is a standard solution to this but I can't find it.

How do you access the volume data from the pixel shader? Based on the link I'm using a Texture3D, which is supported in the shader. What will I do when I want to implement a spacial hashing structure?

How do you determine the color of the pixel once you reach a voxel in the raycasting algorithm? After sampling the color from the volume, I assume you'll want to calculate the normal based off which side you hit it from to do the lighting. How would I apply a texture or shadows to the voxel? I'm just looking to draw each voxel as a cube, like in the image below. I don't care about any smoothing or antialiasing.

I'm not expecting to match that engine in scale but I'd like to at least get a similar appearance.

All of these questions I might be able to figure out on my own with a lot of math and time, but I know they've already been solved. I just can't find a source that explains them clearly.

Hopefully based on this you can tell where I'm at and recommend some reading or more specific search terms. Thanks for any help.

PS: I'm not interested in mesh extraction techniques, just direct volume rendering.

##### Share on other sites
>[color=#1C2837][size=2]1024x1024x64. Ideally it would twice those dimensions.
>I search for leads me to acceleration structures and other advanced concepts
[color=#1C2837][size=2]

[color="#1c2837"]For such "thin" data the [color=#1C2837][size=2]acceleration structures are overkill, just [color="#1c2837"]GPU brute force texture mapping VR would be a better choice; it is not well scalable for thicker data though. There are several "free" GPU based engines suitable for such data... If you go to fat volumes GPU is obsolete multi-core CPU is the way to go...
[color="#1c2837"]

[color="#1c2837"]

##### Share on other sites
Yeah. I was thinking that with such a small volume I may not even need any acceleration structure. But that's something I'll figure out later. For now I'm having trouble finding good resources to just get started.

##### Share on other sites

Yeah. I was thinking that with such a small volume I may not even need any acceleration structure. But that's something I'll figure out later. For now I'm having trouble finding good resources to just get started.

minecraft solves it in a smart way, by generating mesh chunks. I assume by XNA you're talking about the x360 gpu as your main target, it would be faster (if you'll add occlusion culling) to render the faces of your volume.

##### Share on other sites
I have something like that currently implemented, but getting the draw distance I want is pretty much impossible. The Xbox can only handle so many draw calls. So I need to make my chunks extra large, which means they'll take forever to rebuild when they're modified. And the memory requirements of all the vertex buffers is hard to keep down.

I'd hate to spend all my time trying to optimize the mesh extraction approach when It may not even be possible to get it to where I want. I don't know if the direct rendering method will get me there either, but I am still interested in learning the technology.

##### Share on other sites
Directly rendering voxels via raycasting using a single level 3DDDA sounds like it will work. It sounds like you already understand 3DDDA so this should be easy/obvious. Putting it into practice would be to create a format for the voxels. A simple one I started toying with in SlimDX was a 2 level 3DDDA grid traversal. I can give some code snippets which might help you along with a simple design. However directly rendering voxels using a full screen pixel shader is really more of a DX10/11 job than something you'd want to do in older hardware. I'm not sure an Xbox would be fast enough.

I'll describe a basic setup though. You have a chunk info texture that holds offsets to a chunk data texture. You store the state of which chunks are loaded and compression information in the chunk info texture. In the below example we assume a 16 MB texture to hold 256x256x64 chunks. Each chunk info record is 4 bytes consisting of:
[byte] bool chunk type 0 = Empty, 1 = Mixed, 2 = Water, 3 = Lava
[byte] texture index
[short] texture offset
And the chunk data textures are simply just 32x32x32 records with 2 bytes per voxel.
 const int chunkFreeListTextureSize = 4096 * 4096 * 4; const int chunkFreeListTextureCount = 3; const int chunkVoxelSize = 32 * 32 * 32 * 2; // Metadata about each chunk telling if it's loaded int unusedChunkIndex; int unusedChunkCount; int usedChunkIndex; int usedChunkCount; const int chunkCount = chunkFreeListTextureSize * chunkFreeListTextureCount / chunkVoxelSize; ChunkMetaData[] chunkFreeList = new ChunkMetaData[chunkCount]; // Map the unique chunk index to the free list location int[] chunkToFreeList = Enumerable.Repeat(-1, 256 * 256 * 64).ToArray(); // Chunk Info stored in the video card in 2048x2048 32 bit texture. 256x256x64 with 4 bytes per chunk byte[] chunkInfo = new byte[256 * 256 * 64 * 4]; // Chunk Data, stored in the video card in 3 4096x4069 32-bit textures. byte[] chunkData = new byte[chunkFreeListTextureSize * chunkFreeListTextureCount]; 
Initializing the free list of 32x32x32 chunks:
 unusedChunkIndex = 0; unusedChunkCount = chunkCount; usedChunkIndex = -1; usedChunkCount = 0; for (int i = 0; i < chunkCount; ++i) { chunkFreeList.previous = i == 0 ? -1 : i - 1; chunkFreeList.next = i == chunkCount - 1 ? -1 : i + 1; } 
 private int GetChunk(int x, int y, int z) { if (unusedChunkCount == 0) { // No chunks left to be used. Try again later? return -1; } unusedChunkCount--; usedChunkCount++; if (usedChunkIndex == -1) { usedChunkIndex = unusedChunkIndex; unusedChunkIndex = chunkFreeList[unusedChunkIndex].next; chunkFreeList[unusedChunkIndex].previous = -1; chunkFreeList[usedChunkIndex].next = -1; } else { int oldUsedChunkIndex = usedChunkIndex; usedChunkIndex = unusedChunkIndex; unusedChunkIndex = chunkFreeList[unusedChunkIndex].next; if (unusedChunkIndex != -1) chunkFreeList[unusedChunkIndex].previous = -1; chunkFreeList[usedChunkIndex].next = oldUsedChunkIndex; chunkFreeList[oldUsedChunkIndex].previous = usedChunkIndex; } chunkFreeList[usedChunkIndex].x = x; chunkFreeList[usedChunkIndex].y = y; chunkFreeList[usedChunkIndex].z = z; return usedChunkIndex; } private void PutChunk(int chunkIndex) { unusedChunkCount++; usedChunkCount--; if (chunkFreeList[chunkIndex].previous == -1) { usedChunkIndex = chunkFreeList[chunkIndex].next; } else { chunkFreeList[chunkFreeList[chunkIndex].previous].next = chunkFreeList[chunkIndex].next; } if (chunkFreeList[chunkIndex].next != -1) { chunkFreeList[chunkFreeList[chunkIndex].next].previous = chunkFreeList[chunkIndex].previous; } // Add the chunk back to the unused chunk list chunkFreeList[chunkIndex].previous = -1; chunkFreeList[chunkIndex].next = unusedChunkIndex; chunkFreeList[unusedChunkIndex].previous = chunkIndex; unusedChunkIndex = chunkIndex; } private int ChunkUniqueIndex(int x, int y, int z) { return z * 256 * 256 + y * 256 + x; } /// <summary> /// Iterate the AABB region around the position and for any chunk within range and load it /// </summary> /// <param name="position"></param> private void LoadProximityChunks(Vector3 position) { const int size = 6; float radius = (float)Math.Sqrt(2) * ((float)size + 0.5f); int positionX = (int)position.X / 32; int positionY = (int)position.Y / 32; int positionZ = (int)position.Z / 32; int minX = Math.Max(0, positionX - size); int maxX = Math.Min(255, positionX + size); int minY = Math.Max(0, positionY - size); int maxY = Math.Min(255, positionY + size); int minZ = Math.Max(0, positionZ - size); int maxZ = Math.Min(63, positionZ + size); int foo = 0; int bar = 0; for (int z = minZ; z <= maxZ; ++z) { for (int y = minY; y <= maxY; ++y) { for (int x = minX; x <= maxX; ++x) { foo++; if ((x - positionX) * (x - positionX) + (y - positionY) * (y - positionY) + (z - positionZ) * (z - positionZ) <= radius * radius) { bar++; if (chunkToFreeList[ChunkUniqueIndex(x, y, z)] == -1) { LoadChunk(x, y, z); } } } } } } private void UnloadProximityChunks(Vector3 position) { const int size = 7; float radius = (float)Math.Sqrt(2) * ((float)size + 0.5f); int positionX = (int)position.X / 32; int positionY = (int)position.Y / 32; int positionZ = (int)position.Z / 32; for (int iterator = usedChunkIndex; iterator != -1; iterator = chunkFreeList[iterator].next) { int x = chunkFreeList[iterator].x; int y = chunkFreeList[iterator].y; int z = chunkFreeList[iterator].z; if ((x - positionX) * (x - positionX) + (y - positionY) * (y - positionY) + (z - positionZ) * (z - positionZ) > radius * radius) { UnloadChunk(x, y, z, iterator); } } } private void LoadChunk(int x, int y, int z) { // Procedurally generate chunk for now int chunkFreeListIndex = GetChunk(x, y, z); chunkToFreeList[ChunkUniqueIndex(x, y, z)] = chunkFreeListIndex; int chunkDataOffset = chunkFreeListIndex * 32 * 32 * 32 * 2; for (int i = chunkDataOffset; i < chunkDataOffset + 32 * 32 * 32 * 2; i += 2) { // random numbers generated 0, 1, 2, 3 so a 25% chance there will be a voxel at a given position ushort voxelType = random.Next(4) == 0 ? (ushort)0x8001 : (ushort)0x8000; chunkData = (byte)(voxelType >> 8); chunkData[i + 1] = (byte)(voxelType & 0xFF); } // Update chunk info with the change int chunkInfoOffset = ChunkUniqueIndex(x, y, z) * 4; // Chunk Type chunkInfo[chunkInfoOffset + 0] = 1; // Texture Index chunkInfo[chunkInfoOffset + 1] = (byte)ChunkFreeListIndexToTextureIndex(chunkFreeListIndex); // Texture Offset int textureOffset = ChunkFreeListIndexToTextureOffset(chunkFreeListIndex); chunkInfo[chunkInfoOffset + 2] = (byte)(textureOffset >> 8); chunkInfo[chunkInfoOffset + 3] = (byte)(textureOffset & 0xFF); } private void UnloadChunk(int x, int y, int z, int chunkFreeListIndex) { PutChunk(chunkFreeListIndex); chunkToFreeList[ChunkUniqueIndex(x, y, z)] = -1; } private int ChunkFreeListIndexToTextureIndex(int chunkFreeListIndex) { return chunkFreeListIndex / chunkFreeListTextureSize; } private int ChunkFreeListIndexToTextureOffset(int chunkFreeListIndex) { return chunkFreeListIndex % chunkFreeListTextureSize; } private void UploadChunkInfo() { var dataRectangle = chunkInfoSurface.LockRectangle(LockFlags.None); dataRectangle.Data.Write(chunkInfo, 0, 256 * 256 * 64 * 4); chunkInfoSurface.UnlockRectangle(); } 
I can't verify the above code works, but it's shows off the basic structure of managing chunks and changing the chunk info and chunk data textures. I got busy with classes and had to set it aside so I'm not really sure how well it works. I do remember I got a depth map rendering. Texturing is really simple since you just do a modulus operator and since you know which side of the voxel the ray entered you can perform a look-up in a texture for the pixel value to output.

If you're curious the shader looks something like below. In your traversal you traverse similar to regular 3DDDA but when you're at the chunk level and a voxel isn't empty you need to go to the voxel traversal and begin traversing then step back up. This is a fun problem to figure out on paper. It's easy if you look at it as a state graph with 2 states and certain conditions that go from each of the 2 states.
 float aspectRatio; float3x3 cameraRotation; float3 cameraCenter; float focalDistance; float2 tileSize; float2 tileAtlasSize; bool depthMap; texture tileAtlas; texture chunkInfo; texture chunkData0; texture chunkData1; texture chunkData2; sampler tileAtlasSampler = sampler_state { Texture = <tileAtlas>; }; sampler chunkInfoSampler = sampler_state { Texture = <chunkInfo>; }; sampler chunkDataSampler0 = sampler_state { Texture = <chunkData0>; }; sampler chunkDataSampler1 = sampler_state { Texture = <chunkData1>; }; sampler chunkDataSampler2 = sampler_state { Texture = <chunkData2>; }; // Two const boundary limits for chunks and voxels int3 minChunkBoundary = int3(-1, -1, -1); int3 maxChunkBoundary = int3(256, 256, 64); int3 minVoxelBoundary = int3(-1, -1, -1); int3 maxVoxelBoundary = int3(32, 32, 32); float chunkSize = 32.0; float voxelSize = 1.0; // Chunk types float ChunkEmpty = 0; float ChunkMixed = 1; float ChunkWater = 2; float ChunkLava = 3; struct VS_INPUT { float4 Position : POSITION; float4 Color : COLOR0; }; struct VS_OUTPUT { float4 vPosition : POSITION; float4 Position : TEXCOORD0; float4 Color : COLOR0; }; struct PS_OUTPUT { float4 Color : COLOR0; }; VS_OUTPUT VShader(VS_INPUT input) { VS_OUTPUT output; output.vPosition = input.Position; output.Position = input.Position; output.Color = input.Color; return output; } PS_OUTPUT PShader(VS_OUTPUT input) { PS_OUTPUT output; float cameraScale = 0.2; float3 rayPosition = float3(0.0, input.Position.x, input.Position.y / aspectRatio) * float3(0.0, cameraScale, cameraScale); float3 rayDirection = mul(cameraRotation, normalize(rayPosition - float3(-focalDistance * cameraScale, 0.0, 0.0))); // TODO: Test these instead and translate back by the focal distance instead of transforming each pixel position // float3 rayPosition = cameraCenter; // float3 rayDirection = mul(cameraRotation, normalize(float3(focalDistance, input.Position.x, input.Position.y / aspectRatio))); if(all(rayDirection)) { rayPosition = mul(cameraRotation, rayPosition); rayPosition += cameraCenter; int3 chunk = int3(rayPosition / chunkSize); int3 voxel = int3(rayPosition / voxelSize); int3 step = sign(rayDirection); float3 offsetChunkTemp = rayPosition - mul(floor(rayPosition / chunkSize), chunkSize); float3 offsetFromChunkAxis = step == float3(1, 1, 1) ? chunkSize - offsetChunkTemp : offsetChunkTemp; float3 offsetVoxelTemp = rayPosition - mul(floor(rayPosition / voxelSize), voxelSize); float offsetFromVoxelAxis = step == float3(1, 1, 1) ? voxelSize - offsetVoxelTemp : offsetVoxelTemp; float3 tMaxChunk = offsetFromChunkAxis / abs(rayDirection); float3 tDeltaChunk = chunkSize / abs(rayDirection); float3 tMaxVoxel = offsetFromVoxelAxis / abs(rayDirection); float3 tDeltaVoxel = voxelSize / abs(rayDirection); int3 chunkBoundary = step == int3(-1, -1, -1) ? minChunkBoundary : maxChunkBoundary; int3 voxelBoundary = step == int3(-1, -1, -1) ? minVoxelBoundary : maxVoxelBoundary; int lastCrossed = 0; // 0 = x, 1 = y, 2 = z bool chunkLevel = true; // Chunk to voxel traversal loop: while (true) { // Your 3DDDA traversal algorithm that transitions between chunks and voxel levels. } } else { output.Color = float4(1, 0, 1, 1); } return output; } technique voxelTechnique { pass p0 { VertexShader = compile vs_3_0 VShader(); PixelShader = compile ps_3_0 PShader(); } } 
Here's a 2D example of a 2-level 3DDDA algorithm. Not sure if it's optimal though, but it does show the number of taps on the textures required. I've been told that DX9 hardware probably would die performing that many texture look-ups.

Shadows can be performed by ray tracing toward the sun just like regular ray tracing. I believe it would be prohibitively expensive, but I haven't really researched the current methods.

Rendering a full screen quad by the way solves your first question. You can litterally just pass in a very very simple quad into the (-1, -1) to (1, 1) range that is expected so that no transformation is needed in your shader.
 // (3 floats per Vector4) * (4 bytes for each float) + (4 bytes for each integer color) = 20 vertices = new VertexBuffer(device, 4 * 20, Usage.WriteOnly, VertexFormat.None, Pool.Managed); vertices.Lock(0, 0, LockFlags.None).WriteRange(new[] { new Vertex() { Position = new Vector4(-1, -1, 0, 1), Color = new Color4(1, 1, 0, 0).ToArgb() }, new Vertex() { Position = new Vector4(-1, 1, 0, 1), Color = new Color4(1, 0, 1, 0).ToArgb() }, new Vertex() { Position = new Vector4(1, 1, 0, 1), Color = new Color4(1, 0, 0, 1).ToArgb() }, new Vertex() { Position = new Vector4(1, -1, 0, 1), Color = new Color4(1, 1, 0, 1).ToArgb() } }); vertices.Unlock(); var vertexElements = new[] { new VertexElement(0, 0, DeclarationType.Float4, DeclarationMethod.Default, DeclarationUsage.Position, 0), new VertexElement(0, 16, DeclarationType.Color, DeclarationMethod.Default, DeclarationUsage.Color, 0), VertexElement.VertexDeclarationEnd }; vertexDeclaraction = new VertexDeclaration(device, vertexElements); 

##### Share on other sites
Wow thanks this is really helpful! I've just about got something working. I don't understand how the rayDirection is calculated. I assume cameraScale and focalDistance are somehow related to fov. How can I determine the proper values based on fov, or is there a way to use a projection matrix instead?

##### Share on other sites

So you have this setup and you want to scale it so that the camera scale is smaller such that the rays fire from a plane that represent a smaller screen. This camera scaling is merely so that the camera plane doesn't clip into objects very easily if you're using a world with like 1.0 = 1 meter. If you can imagine it the screen is 2x2 meters (ignoring the aspect ratio) and rotates around its center. Now this 2x2 meter quad will probably clip into things if it isn't scaled.

FOV = atan2(focalDistance, 1) * 2:
or in a more useful notation:
focalDistance = tan(FOV / 2);

So if FOV is 90 degrees then focalDistance should be 1.

As for the ray direction you can imagine that the screen is split into a grid of pixels with each having a normalized (length of 1) ray emitting from the surface. To construct the ray you take the pixel position which happens to the be the input into the pixel shader and subtract it by a position located right behind the plane (defined by the focal distance). Rotating the camera rotates all of the ray directions the same way.

Also here's a fun image:

It describes the convention used in that code. Z is up and X is to the right with Y going into the screen. Most of the problems you'll have can be easily solved by just drawing the situations out on paper.

##### Share on other sites
Alright! I finally made something that looks how I want it to:

This is at 640x360 on my PC. I get about 20 fps on the Xbox. I'm not using the chunk structure you posted yet, it's just one 256^3 volume. With the layout of my data I don't think a 2 level traversal would have any benefits when the camera is at ground level. There are probably zero chunks in there that have homogeneous data. My chunk size would have to be like 4^3 to have any benefit, but then I'd be passing in a large amount of textures. I've also realized that I really don't know my 3d math well enough. Every small problem I run into takes forever to figure out. I think next semester I'll take that 3D math and physics course I've been avoiding. Thanks for the help. I might try adding textures later, but I think my practical use of this is going to be pretty limited for now.