• 12
• 11
• 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 [solved]D3D's RHW and OpenGL's W

This topic is 2930 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

--I've rewritten this topic in hopes that someone will reply as I am in need of help desperetly. ========================================================== Solution: Call glLoadIdentity(); after clearing the buffers at the beginning of the scene fixed my problem (which was not anything to do with RHW, but screen co-ordinates. ========================================================== Though this topic blurs between the two API's I'm asking for an explanation of the difference between the two API's seemingly similar co-ordinate component. Why? In a game I have the source-code to that was made in 1999 and uses Direct3D7, Glide 3 and a Software Rasterizer, the fan community have encountered problems with all three renderers at some stage, most people with older machines with 32-bit CPU's and old nVidia cards (such as my GeForce 6200A) don't have a problem with the D3D7 or Software renderers, but the problems vary and there have been too many reports with a lack of information (from a large number of people who don't even know what the difference between add-on and onboard) for us to narrow down the causes. So what I did to counter the problems was propose to my teammates that we rebuild the Renderer's a Direct3D9 and OpenGL Renderer each, would replace the old ones and hopefully kill all renderer related problems. Also note that the game has all three renderers in the same project and uses an #ifdef pre-processor check to see if the current Build-Target is supposed to use the Render###.CPP file the compiler is checking, it's an old and inefficient way but right now we aren't up to the task of rewriting large portions of code to implement a better solution. Now there are many sources that say a lot of things, so far I've read that Glide and OpenGL are similar and while I agree, it seems only the way you write applicaiton code for them are similar, while OpenGL and Direct3D9 now share a lot of similarities. What I began doing is rewriting the 3Dfx Glide code with OpenGL code and since the original renderers don't make use of the Projection or World matrices, we're stuck with the D3D RHW and Glide's messy equivilent's the z,oow,ooz (oow is for W-Buffering and ooz for Z-Buffering IIRC, but I don't see a purpose for W-Buffering in the game since the code seems to indicate the use of only the Z-Buffer) Now... I've done a bit of googling for resources and come up kind of dry for explanations on the differences between the D3D RHW and OpenGL W values of Vertices and am hoping someone here might be able to clear it up for me as I'd like to write these new renderer's ASAP and there are a lot of people eagerly waiting for modern Hardware support. The best I've managed to scrounge up, sadly, is the following:
Quote:
 RHW is often 1 divided by the distance from the origin to the object along the z-axis.
From my understanding (and please correct me if I am wrong) that would mean that RHW is:
float origin_z = 0.f;
float vert_z = 10.0f;

float rhw = 1.0f / (vert_z - origin_z);

result: rhw = 0.1f


Now I've tried using the same data for the OpenGL renderer as the D3D renderer but I'm not getting much more than either a mess of triangles that have a heart attack all over the screen, or no triangles at all. RHW and W equal to 1.0f seem to do the same thing if I provide x,y,z values that lie within the view range (except OpenGL's 2D floating point origin is in the middle of the screen (0.0f,0.0f) where as D3D's is not) Anyway hopefully someone reads this topic this time around and can help me out as I'm stuck Trial and Erroring (which is not working out so well with a complete game engine I'm afraid) ~James [Edited by - RexHunter99 on March 16, 2010 9:05:08 AM]

##### Share on other sites
-Bump-

I hate bumping but I really need help with this, I've spent the last 3 days trying to figure it out through Trial and Error but nothing beats knowing the correct answer straight up.

I don't know if the topic scared anyone away or if I've just gotten accidentally unnoticed, but the help is very very much needed and appreciated.

##### Share on other sites
I know Opengl expects a certain triangle winding, counter clock wise by default, for a triangle to be considered forward facing. Directx of course expects the opposite. This could mean that triangles are being culled in opengl that would not be culled in direct X and vise verse. As far as actual coordinates being off I don't know that much about DX OGL differences sorry.

##### Share on other sites
Why can't you just use view and projection matrices like everybody else? There's no need to mess with all this RHW stuff, just use standard perspective calculation and you're done. AFAIK Triangle winding is the same in DX and OGL because its possible to import models from one to the other without issues.

##### Share on other sites
I'll post a picture of the OpenGL renderer in action (so you can see what I mean) note that in order to even see the triangles, I had to fix the first vertex to the co-ordinates: 0.0f, 0.0f, 0.0f, 1.0f (x, y, z, w)

^^^ Note that the pixels that are not red (that area to the lower left) is the background color I defined when I cleared the color buffer.)

Quote:
 Original post by stonemetalI know Opengl expects a certain triangle winding, counter clock wise by default, for a triangle to be considered forward facing. Directx of course expects the opposite. This could mean that triangles are being culled in opengl that would not be culled in direct X and vise verse. As far as actual coordinates being off I don't know that much about DX OGL differences sorry.

Yes, OpenGL expects the opposite triangle winding to Direct3D, OpenGl requires Anti-Clock-Wise and Direct3D requires Clock-Wise, I've accommodated for this in the renderers (OpenGl will now take in Direct3D information, for testing purposes right now, I'll properly fix this problem at a later stage)

Quote:
 Original post by Momoko_FanWhy can't you just use view and projection matrices like everybody else? There's no need to mess with all this RHW stuff, just use standard perspective calculation and you're done. AFAIK Triangle winding is the same in DX and OGL because its possible to import models from one to the other without issues.

Oh snappy snappy, you know you could have worded this reply in a nicer way? You make it sound like I'm a stupid idiot. I would have tried to use the 'normal' way to do it, but like I've said, the code is very hard to mess around with, right now I'm only replacing code with updated code that uses Direct3D9 and OpenGL ( my problem lies with the OpenGL though) The game's original creators have already processed all the projection data prior to the rendering stage, or as much of it as possible. I have to deal with this RHW stuff because otherwise I'd have to do a complete code overhaul and my position on the team is the graphical programmer, I work on the 3D code because I can visualize a 3D scene in my head rather easily with the given information.

And you're wrong, D3D and OpenGL have different triangle winding by default, you can change how they deal with that if you enable backface culling and change the winding then, but that's a short-term unpreferred fix. Also OpenGL and Direct3D have different co-ordinate systems, one is Left-Hand and the other is Right-Hand, I think I've accomodated for this already though... not 100% sure because I can't quite tell until this RHW stuff is down.

Just going to say this for anyone else going to tell me to do this the 'normal/modern' way with the Perspective/Ortho matrix functions:
If anyone else wants to be a smart-arse like Momoko_Fan was, then why don't you try rewriting over 20,000 lines of code for me? remember you have to accommodate for at least two different graphics APIs and comment most of the functions as you go along so you/others know what they do?

[Edited by - RexHunter99 on March 12, 2010 9:10:03 AM]

##### Share on other sites
Quote:
 Original post by RexHunter99Also OpenGL and Direct3D have different co-ordinate systems, one is Left-Hand and the other is Right-Hand, I think I've accomodated for this already though... not 100% sure because I can't quite tell until this RHW stuff is down.

Silly question, but sometimes the silly stuff is what gets us... do you mean you transposed the [4]x[4] D3D matrix in order to get an OpenGL [16] element matrix?

Most of the time thats all I have to do when "translating" matrix operations intended for D3D to OpenGL.

Good Luck.

##### Share on other sites
No, my quick fix solution was to inverse the Y co-ordinate so it'd appear in the 'correct place' or appear in the same place as it would in Direct3D, anyway that's besides the point, I want to know if there's a difference between OpenGL and Direct3D's W and RHW values and if there is, what the difference is so I can accommodate for it in the game code.

##### Share on other sites
Quote:
 Original post by RexHunter99No, my quick fix solution was to inverse the Y co-ordinate so it'd appear in the 'correct place' or appear in the same place as it would in Direct3D, anyway that's besides the point, I want to know if there's a difference between OpenGL and Direct3D's W and RHW values and if there is, what the difference is so I can accommodate for it in the game code.

I am not sure if there is a difference, shouldn't be, I usually just leave W as 1 in OpenGL, I think the OpenGL ModelView matrix is 2 separate matrices in D3D, so maybe you should factor that in.

Perhars this would help:
Quote:
 9.011 How are coordinates transformed? What are the different coordinate spaces?Object Coordinates are transformed by the ModelView matrix to produce Eye Coordinates.Eye Coordinates are transformed by the Projection matrix to produce Clip Coordinates.Clip Coordinate X, Y, and Z are divided by Clip Coordinate W to produce Normalized Device Coordinates.Normalized Device Coordinates are scaled and translated by the viewport parameters to produce Window Coordinates.Object coordinates are the raw coordinates you submit to OpenGL with a call to glVertex*() or glVertexPointer(). They represent the coordinates of your object or other geometry you want to render.Many programmers use a World Coordinate system. Objects are often modeled in one coordinate system, then scaled, translated, and rotated into the world you're constructing. World Coordinates result from transforming Object Coordinates by the modelling transforms stored in the ModelView matrix. However, OpenGL has no concept of World Coordinates. World Coordinates are purely an application construct.Eye Coordinates result from transforming Object Coordinates by the ModelView matrix. The ModelView matrix contains both modelling and viewing transformations that place the viewer at the origin with the view direction aligned with the negative Z axis.Clip Coordinates result from transforming Eye Coordinates by the Projection matrix. Clip Coordinate space ranges from -Wc to Wc in all three axes, where Wc is the Clip Coordinate W value. OpenGL clips all coordinates outside this range.Perspective division performed on the Clip Coordinates produces Normalized Device Coordinates, ranging from -1 to 1 in all three axes.Window Coordinates result from scaling and translating Normalized Device Coordinates by the viewport. The parameters to glViewport() and glDepthRange() control this transformation. With the viewport, you can map the Normalized Device Coordinate cube to any location in your window and depth buffer.For more information, see the OpenGL Specification, Figure 2.6.

If you're dealing with matrices though, you shouldn't just mirror Y, you should transpose the matrices because of how they are accessed, OpenGL defines them as a one dimension array whereas D3D access them as a 4x4 two dimensional array, mapping one to the other doesn't leave the elements on the proper positions, check point 9.005 on the link I posted above.

##### Share on other sites
Just passing through briefly.. might have some code you can look at later that might help?

Aliens Vs Predator original D3D 5/6 code, the linux OpenGL renderer update for said game and my D3D9 equivelant. Source code repository for linux port doesn't seem to be online at the moment so I can't just link you at the moment.

Out of curiosity, what game is it? If it's one I like i'd be interested in helping :)

##### Share on other sites
Quote:
 Original post by sirlemonheadJust passing through briefly.. might have some code you can look at later that might help? Aliens Vs Predator original D3D 5/6 code, the linux OpenGL renderer update for said game and my D3D9 equivelant. Source code repository for linux port doesn't seem to be online at the moment so I can't just link you at the moment.Out of curiosity, what game is it? If it's one I like i'd be interested in helping :)

D3D 5/6 and D3D7 are quite similar despite how far they came ;) After that D3D just went up exponentionally...

Urm that might be nice actually, thanks, when you can could you show me some code? Would be a great help (I'm just implementing the basic HUD UI function equivalents now, hopefully glDrawPixels isn't too slow to hamper gameplay)

The game is Carnivores 2, created by a company known as Action-Forms, currently, Tatem Games a mobile gaming company has a license to make an iPhone App called Carnivores: Dinosaur Hunter which is set for release this year. Action-Forms gave us the source-code and we were dismayed to find that they'd overwritten the first game's code with the second game's code and also lost the menu code (the game compiles into a .REN file (a renamed .EXE file) that the menu executes after you've selected your level, dinosaurs and weapons.

You may or may not have heard of it ;)