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• 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 Upgraded from GFX5200 to 9800 Pro, need help!

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Ive got myself a Radeon 9800 Pro to replace my old GeForce 5200, anyway in my main development project (a space combat/exploration game) I draw the sun and lense flares with 2d textured quads and blending enabled which worked fine on the old card but on the ATI I can see the part of the square that should be transparent, i.e. the circle which I want to see and a dim square around it. I'll post code if needed but my main concern is that I thought opengl was more or less standardised across different cards. I realise that they are different manufacturers and drivers etc but Im not using any fancy extensions or anything just basic blending and textured quads and theres a big difference in what each card produces. Please help, I've lost a little faith in open gl!!!

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Quote:
 Original post by comedypedroIve got myself a Radeon 9800 Pro to replace my old GeForce 5200, anyway in my main development project (a space combat/exploration game) I draw the sun and lense flares with 2d textured quads and blending enabled which worked fine on the old card but on the ATI I can see the part of the square that should be transparent, i.e. the circle which I want to see and a dim square around it. I'll post code if needed but my main concern is that I thought opengl was more or less standardised across different cards. I realise that they are different manufacturers and drivers etc but Im not using any fancy extensions or anything just basic blending and textured quads and theres a big difference in what each card produces. Please help, I've lost a little faith in open gl!!!

It is standardized. What probably happened is that you were relying on a specific artifact of one card that is allowed by the standardization. It's like relying on a Microsoft VC++ specific or GCC specific not-quite-bug.

It is most likely your texture or rendering code is not quite right, you just didn't notice it as much on the old card.

frob.

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Thanks for your reply. I understand what you mean when you compare it to relying on MS VC to be exactly the same as the C++ standard, but the output from the two cards is very different indeed and I would have thought the opengl standardisations (if thats the right word) would be tighter. I mean if I was running an ancient TNT card or something and went up to a state of the art SLI setup I'd except some differences but the 5200 and the 9800 are same generation boards.

Im going to play around with it a bit to get it working and Im also going to keep the current build to try out on other machines/cards.

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This sounds like it could be something like having alternate texel centers turned on for one of your cards and not the other. Look in your drivers for something like that; I can't remember if it is in both ATI and NVIDIA drivers or just one of them. Having this turned on makes OpenGL sample from the center of a texel instead of the bottom-left corner and depending on your wrap mode this could end up making the texture blend with the border on one card and not on the other if you are using bilinear filtering.

Other than that I think we will need to see some code and possibly a screenshot.

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I think I know what youre talking about and I'll look into the driver settings but its the whole square I can see not just the border. I'm looking into posting a picture (can I upload a pic to GameDev or do I need to find somewhere else to host??) and then I'll post the code too.

Cheers

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What is your near/far plane set to? This might be a depth precision problem. Also you might want to try and disable the depth buffer when rendering that texture and see if that helps...

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Quote:
 Original post by comedypedroThanks for your reply. I understand what you mean when you compare it to relying on MS VC to be exactly the same as the C++ standard, but the output from the two cards is very different indeed and I would have thought the opengl standardisations (if thats the right word) would be tighter.

That has nothing to do with standarization. If you use an API in an incorrect way or rely on undefined behaviour, then the results will be unpredictable. The standard is very clear on what is defined and what not. In the C example, this is like relying on the value of an undefined variable, and then complaining about the language being non-standarized, when your code crashes.

Either your background alpha is not completely transparent (ie. zero), and your 5200 allocated an RGBA5551 texture (essentially making it transparent by truncation), while the 9800 allocates an RGBA8 texture.

Or you have done something wrong with the texenv combine pipeline, and have some non-zero alpha leak in somewhere. Post your code.

Also, did you enable fullscreen antialiasing on the 9800 ?

Quote:
 Original post by KalidorThis sounds like it could be something like having alternate texel centers turned on for one of your cards and not the other. Look in your drivers for something like that; I can't remember if it is in both ATI and NVIDIA drivers or just one of them. Having this turned on makes OpenGL sample from the center of a texel instead of the bottom-left corner

OpenGL samples from the center by default.

Quote:
 Original post by MARS_999What is your near/far plane set to? This might be a depth precision problem.

From his problem description, this is most definitely not a depthbuffer problem.

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Quote:
 Original post by Yann LThat has nothing to do with standarization. If you use an API in an incorrect way or rely on undefined behaviour, then the results will be unpredictable. The standard is very clear on what is defined and what not. In the C example, this is like relying on the value of an undefined variable, and then complaining about the language being non-standarized, when your code crashes....From his problem description, this is most definitely not a depthbuffer problem.

On the first bit of quote, for the OP, there are three thingsthe standard allows: DB, IB, and UB. Defined behavior, implementation defined behavior, and undefined behavior.

Obviously the bug is relying on either IB or UB. And I agree that it isn't a depth buffer problem based on the description. It is almost certainly a texture rasterization issue dealing with the alpha values.

Without seeing code, though, it's just a guess.

My first thought was exactly what you mentioned. It might be from the conversion to the card's internal color format (the 5551 conversion), either through an incorrect internal format or source image format. Those conversions and supported formats are implementation defined. I doubt this would be the cause, though, since both cards are great and handling that if the rendering contexts are similarly set.

My second thought was that it was a driver setting. Most video card drivers allow forcing certain values.

My third thought was that the app is incorrectly enumerating and obtaining the rendering context, perhaps something obtained in the first card's context was not specified as a requirement, so the second card didn't provide it because it didn't have to.

My fourth thought was that the programmer might be using the GL in a way that is undefined, giving bad results.

I'm sure I could come up with a bunch more, but without seeing the code, it's anybody's guess.

frob.

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Thanks very much for all your replys, I was worried that no one would have a clue about what I was on about. Im now looking on this as a learning experience and I guess things like this are why PC developers have such large testing and quality assurance teams!! It also highlights a big advantage of consoles, i.e. if it works on one playstation it'll work on them all!!

Right so here are some photos of the problem :

Pic 1

Pic 2

And what I think/hope is the relevent code :

The texture code :
glPixelStorei(GL_UNPACK_ALIGNMENT, 4);	glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, iWidth, iHeight, 0, GL_ALPHA, GL_UNSIGNED_BYTE, pImageData);

Probably not needed but here is the rendering code :
		float fAlpha = 1 - fLength / 1280;		fAlpha -= 0.5;		glEnable(GL_BLEND);		glBlendFunc(GL_SRC_ALPHA, GL_DST_ALPHA);		glDisable(GL_LIGHTING);		glDisable(GL_DEPTH_TEST);		glEnable(GL_TEXTURE_2D);		glBindTexture(GL_TEXTURE_2D, HaloTex);		glColor4f(1.0f, 0.6f, 0.6f, fAlpha);		pApp->Draw2dOrthoQuad(vPos.x + vScreenCentre.x, vPos.y + vScreenCentre.y, 50, 50, DRAW_PARAM_CENTRE);		glColor4f(0.5f, 1.0f, 0.5f, fAlpha);		pApp->Draw2dOrthoQuad(vPos2.x + vScreenCentre.x, vPos2.y + vScreenCentre.y, 70, 70, DRAW_PARAM_CENTRE);		glColor4f(0.5f, 0.5f, 1.0f, fAlpha - 0.1f);		pApp->Draw2dOrthoQuad(vPos3.x + vScreenCentre.x, vPos3.y + vScreenCentre.y, 150, 150, DRAW_PARAM_CENTRE);		glBindTexture(GL_TEXTURE_2D, SpotTex);		glColor4f(0.5f, 0.5f, 1.0f, fAlpha);		pApp->Draw2dOrthoQuad(vPos4.x + vScreenCentre.x, vPos4.y  + vScreenCentre.y, 20, 20, DRAW_PARAM_CENTRE);		glColor4f(0.5f, 1.0f, 0.5f, fAlpha - 0.1f);		pApp->Draw2dOrthoQuad(vPos5.x + vScreenCentre.x, vPos5.y + vScreenCentre.y, 20, 20, DRAW_PARAM_CENTRE);		glColor4f(1.0f, 0.5f, 0.5f, fAlpha);		pApp->Draw2dOrthoQuad(vPos6.x + vScreenCentre.x, vPos6.y + vScreenCentre.y, 20, 20, DRAW_PARAM_CENTRE);		glBindTexture(GL_TEXTURE_2D, SunTex);		fAlpha -= 0.1f;		glPushMatrix();						glTranslatef(vLightPos.x, vLightPos.y, 0);						glColor4f(1.0f, 0.0f, 0.0f, fAlpha);			glRotatef(fLength, 0.0f, 0.0f, 1.0f);			pApp->Draw2dOrthoQuad(0, 0, 600 - fLength, 600 - fLength, DRAW_PARAM_CENTRE);			glColor4f(0.0f, 1.0f, 0.0f, fAlpha);			glRotatef(fLength * 0.5, 0.0f, 0.0f, 1.0f);			pApp->Draw2dOrthoQuad(0, 0, 600 - fLength, 600 - fLength, DRAW_PARAM_CENTRE);			glColor4f(0.0f, 0.0f, 1.0f, fAlpha);			glRotatef(fLength * 0.2, 0.0f, 0.0f, 1.0f);			pApp->Draw2dOrthoQuad(0, 0, 600 - fLength, 600 - fLength, DRAW_PARAM_CENTRE);		glPopMatrix();

Any help or suggestions very welcome and thanks again