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OpenGL Converting OpenGL Frustum Culling Tutorial to Direct3D? Help, please ...

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Hey there. Thanks for reading my post, and I hope you can offer me some help. I am trying to learn, and get the hang of, frustum culling. I currently have the DirectX 8 SDK. I haven''t taken the time to get the DX 9 SDK . Anyhow, I wanted to try something new, so I went looking for frustum culling tutorials. I didn''t really find anything DirectX (D3D) specific, so I decided I would convert an OpenGL frustum culling tutorial. Well, here''s the problem. I don''t think I am calculating the frustum''s planes correctly. Here is the OpenGL code:
void CFrustum::CalculateFrustum(float *md, float *proj)
{
// Error checking.

if(md == 0 || proj == 0)
return;

// Create the clip.

float clip[16] = {0};

clip[0] = md[0] * proj[0] + md[1] * proj[4] + md[2] * proj[8]  + md[3] * proj[12];
clip[1] = md[0] * proj[1] + md[1] * proj[5] + md[2] * proj[9]  + md[3] * proj[13];
clip[2] = md[0] * proj[2] + md[1] * proj[6] + md[2] * proj[10] + md[3] * proj[14];
clip[3] = md[0] * proj[3] + md[1] * proj[7] + md[2] * proj[11] + md[3] * proj[15];

clip[4] = md[4] * proj[0] + md[5] * proj[4] + md[6] * proj[8]  + md[7] * proj[12];
clip[5] = md[4] * proj[1] + md[5] * proj[5] + md[6] * proj[9]  + md[7] * proj[13];
clip[6] = md[4] * proj[2] + md[5] * proj[6] + md[6] * proj[10] + md[7] * proj[14];
clip[7] = md[4] * proj[3] + md[5] * proj[7] + md[6] * proj[11] + md[7] * proj[15];

clip[8]  = md[8] * proj[0] + md[9] * proj[4] + md[10] * proj[8]  + md[11] * proj[12];
clip[9]  = md[8] * proj[1] + md[9] * proj[5] + md[10] * proj[9]  + md[11] * proj[13];
clip[10] = md[8] * proj[2] + md[9] * proj[6] + md[10] * proj[10] + md[11] * proj[14];
clip[11] = md[8] * proj[3] + md[9] * proj[7] + md[10] * proj[11] + md[11] * proj[15];

clip[12] = md[12] * proj[0] + md[13] * proj[4] + md[14] * proj[8]  + md[15] * proj[12];
clip[13] = md[12] * proj[1] + md[13] * proj[5] + md[14] * proj[9]  + md[15] * proj[13];
clip[14] = md[12] * proj[2] + md[13] * proj[6] + md[14] * proj[10] + md[15] * proj[14];
clip[15] = md[12] * proj[3] + md[13] * proj[7] + md[14] * proj[11] + md[15] * proj[15];

// Calculate the right side of the frustum.

Frustum[0].a = clip[3]  - clip[0];
Frustum[0].b = clip[7]  - clip[4];
Frustum[0].c = clip[11] - clip[8];
Frustum[0].d = clip[15] - clip[12];

// Calculate the left side of the frustum.

Frustum[1].a = clip[3]  + clip[0];
Frustum[1].b = clip[7]  + clip[4];
Frustum[1].c = clip[11] + clip[8];
Frustum[1].d = clip[15] + clip[12];

// Calculate the bottom side of the frustum.

Frustum[2].a = clip[3]  + clip[1];
Frustum[2].b = clip[7]  + clip[5];
Frustum[2].c = clip[11] + clip[9];
Frustum[2].d = clip[15] + clip[13];

// Calculate the top side of the frustum.

Frustum[3].a = clip[3]  - clip[1];
Frustum[3].b = clip[7]  - clip[5];
Frustum[3].c = clip[11] - clip[9];
Frustum[3].d = clip[15] - clip[13];

// Calculate the far side of the frustum.

Frustum[4].a = clip[3]  - clip[2];
Frustum[4].b = clip[7]  - clip[6];
Frustum[4].c = clip[11] - clip[10];
Frustum[4].d = clip[15] - clip[14];

// Calculate the near side of the frustum.

Frustum[5].a = clip[3]  + clip[2];
Frustum[5].b = clip[7]  + clip[6];
Frustum[5].c = clip[11] + clip[10];
Frustum[5].d = clip[15] + clip[14];

// Normalize the sides of the frustum.

NormalizeFrustum();
}

''md'' is retrieved with ''glGetFloatv(GL_MODELVIEW_MATRIX, model);'', while ''proj'' is retrieved with ''glGetFloatv(GL_PROJECTION_MATRIX, proj);''. ''CFrustum::CalculateFrustum()'' is then called, passing those two variables as the parameters. And if I am right, I believe ''GL_MODELVIEW_MATRIX'' is just the view matrix (D3D: ''D3DTS_VIEW''). It''s using the view (I think that is what ''md'' is) and the projection matrices to calculate the planes of the frustum. Now, here''s my code:
void CFrustum::CalculateFrustum(D3DXMATRIX *matView, D3DXMATRIX *matProj)
{
// TODO: Calculate the view frustum from the matrices specified

assert(matView != NULL);      // Check the view matrix

assert(matProj != NULL);      // Check the projection matrix

// Now we create the clip

float fClip[16] = { 0 };      // Array of the clip data

// Initialize the clip data

fClip[0]  = matView->_11 * matProj->_11 + matView->_12 * matProj->_21 + matView->_13 * matProj->_31 + matView->_14 * matProj->_41;
fClip[1]  = matView->_11 * matProj->_12 + matView->_12 * matProj->_22 + matView->_13 * matProj->_32 + matView->_14 * matProj->_42;
fClip[2]  = matView->_11 * matProj->_13 + matView->_12 * matProj->_23 + matView->_13 * matProj->_33 + matView->_14 * matProj->_43;
fClip[3]  = matView->_11 * matProj->_14 + matView->_12 * matProj->_24 + matView->_13 * matProj->_34 + matView->_14 * matProj->_44;

fClip[4]  = matView->_21 * matProj->_11 + matView->_22 * matProj->_21 + matView->_23 * matProj->_31 + matView->_24 * matProj->_41;
fClip[5]  = matView->_21 * matProj->_12 + matView->_22 * matProj->_22 + matView->_23 * matProj->_32 + matView->_24 * matProj->_42;
fClip[6]  = matView->_21 * matProj->_13 + matView->_22 * matProj->_23 + matView->_23 * matProj->_33 + matView->_24 * matProj->_43;
fClip[7]  = matView->_21 * matProj->_14 + matView->_22 * matProj->_24 + matView->_23 * matProj->_34 + matView->_24 * matProj->_44;

fClip[8]  = matView->_31 * matProj->_11 + matView->_32 * matProj->_21 + matView->_33 * matProj->_31 + matView->_34 * matProj->_41;
fClip[9]  = matView->_31 * matProj->_12 + matView->_32 * matProj->_22 + matView->_33 * matProj->_32 + matView->_34 * matProj->_42;
fClip[10] = matView->_31 * matProj->_13 + matView->_32 * matProj->_23 + matView->_33 * matProj->_33 + matView->_34 * matProj->_43;
fClip[11] = matView->_31 * matProj->_14 + matView->_32 * matProj->_24 + matView->_33 * matProj->_34 + matView->_34 * matProj->_44;

fClip[12] = matView->_41 * matProj->_11 + matView->_42 * matProj->_21 + matView->_43 * matProj->_31 + matView->_44 * matProj->_41;
fClip[13] = matView->_41 * matProj->_12 + matView->_42 * matProj->_22 + matView->_43 * matProj->_32 + matView->_44 * matProj->_42;
fClip[14] = matView->_41 * matProj->_13 + matView->_42 * matProj->_23 + matView->_43 * matProj->_33 + matView->_44 * matProj->_43;
fClip[15] = matView->_41 * matProj->_14 + matView->_42 * matProj->_24 + matView->_43 * matProj->_34 + matView->_44 * matProj->_44;

// Calculate the right side of the frustum

m_Frustum[0].a = fClip[3]  - fClip[0];
m_Frustum[0].b = fClip[7]  - fClip[4];
m_Frustum[0].c = fClip[11] - fClip[8];
m_Frustum[0].d = fClip[15] - fClip[12];

// Calculate the left side of the frustum

m_Frustum[1].a = fClip[3]  + fClip[0];
m_Frustum[1].b = fClip[7]  + fClip[4];
m_Frustum[1].c = fClip[11] + fClip[8];
m_Frustum[1].d = fClip[15] + fClip[12];

// Calculate the bottom side of the frustum

m_Frustum[2].a = fClip[3]  + fClip[1];
m_Frustum[2].b = fClip[7]  + fClip[5];
m_Frustum[2].c = fClip[11] + fClip[9];
m_Frustum[2].d = fClip[15] + fClip[13];

// Calculate the left side of the frustum

m_Frustum[3].a = fClip[3]  - fClip[1];
m_Frustum[3].b = fClip[7]  - fClip[5];
m_Frustum[3].c = fClip[11] - fClip[9];
m_Frustum[3].d = fClip[15] - fClip[13];

// Calculate the far side of the frustum

m_Frustum[4].a = fClip[3]  - fClip[2];
m_Frustum[4].b = fClip[7]  - fClip[6];
m_Frustum[4].c = fClip[11] - fClip[10];
m_Frustum[4].d = fClip[15] - fClip[14];

// Calculate the near side of the frustum

m_Frustum[5].a = fClip[3]  + fClip[2];
m_Frustum[5].b = fClip[7]  + fClip[6];
m_Frustum[5].c = fClip[11] + fClip[10];
m_Frustum[5].d = fClip[15] + fClip[14];

NormalizeFrustum();     // Normalize the sides of the frustum

}

I''m sorry if you need more information (other functions in the ''CFrustum'' class, etc.) but I think that''s all you need to know. If anything else is needed, let me know =). Anyhow, I don''t think I am calculating the frustum correctly (filling the ''clip[16]'' array) with the correct information. I just thought that ''md[0]'' would equal ''matView->_11''. If you can help me solve this problem, I would really appreciate it. =) Thanks very much, Matt U.

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right heres what the matrixes are in D3D:

Projection Matrix is the screen space matrix, it is declared during setup usually, i think that will be usefull to you..

View Matrix is the camera view so to speak, it is what your looking at so to speak

World Matrix is basically the modelview matrix, each 3d object such as a mesh or shape should have its own world matrix...

So if you would be using the ModelView Matrix in OpenGL i think in D3D you would use D3DTS_WORLD matrix for that...

im not too sure about it though, i aint done frustrum culling and i was asking about matrixes on here the other day... so best listen to someone else...LOL but theres my input..haha

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LoL. Well, thanks. I''ll try it out when I get a chance.

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Hey, thanks for the reply, and the attempt to help me, but that didn''t work. If you or anyone can offer me some help, please do.

Thanks,
Matt U.

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Introduction
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There are at least four APIs (Direct3D11, Direct3D12, OpenGL/GLES, Vulkan, plus Apple's Metal for iOS and osX platforms) that a cross-platform 3D application may need to support. Writing separate code paths for all APIs is clearly not an option for any real-world application and the need for a cross-platform graphics abstraction layer is evident. The following is the list of requirements that I believe such layer needs to satisfy:
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Overview
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Render device (IRenderDevice  interface) is responsible for creating all other objects (textures, buffers, shaders, pipeline states, etc.).
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API Basics
Creating Resources
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ShaderCreationAttribs Attrs; Attrs.Desc.Name = "MyPixelShader"; Attrs.FilePath = "MyShaderFile.fx"; Attrs.SearchDirectories = "shaders;shaders\\inc;"; Attrs.EntryPoint = "MyPixelShader"; Attrs.Desc.ShaderType = SHADER_TYPE_PIXEL; Attrs.SourceLanguage = SHADER_SOURCE_LANGUAGE_HLSL; BasicShaderSourceStreamFactory BasicSSSFactory(Attrs.SearchDirectories); Attrs.pShaderSourceStreamFactory = &BasicSSSFactory; ShaderVariableDesc ShaderVars[] = {     {"g_StaticTexture", SHADER_VARIABLE_TYPE_STATIC},     {"g_MutableTexture", SHADER_VARIABLE_TYPE_MUTABLE},     {"g_DynamicTexture", SHADER_VARIABLE_TYPE_DYNAMIC} }; Attrs.Desc.VariableDesc = ShaderVars; Attrs.Desc.NumVariables = _countof(ShaderVars); Attrs.Desc.DefaultVariableType = SHADER_VARIABLE_TYPE_STATIC; StaticSamplerDesc StaticSampler; StaticSampler.Desc.MinFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MagFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MipFilter = FILTER_TYPE_LINEAR; StaticSampler.TextureName = "g_MutableTexture"; Attrs.Desc.NumStaticSamplers = 1; Attrs.Desc.StaticSamplers = &StaticSampler; ShaderMacroHelper Macros; Macros.AddShaderMacro("USE_SHADOWS", 1); Macros.AddShaderMacro("NUM_SHADOW_SAMPLES", 4); Macros.Finalize(); Attrs.Macros = Macros; RefCntAutoPtr<IShader> pShader; m_pDevice->CreateShader( Attrs, &pShader );
Creating the Pipeline State Object
After all required shaders are created, the rest of the fields of the PipelineStateDesc structure provide depth-stencil, rasterizer, and blend state descriptions, the number and format of render targets, input layout format, etc. For instance, rasterizer state can be described as follows:
PipelineStateDesc PSODesc; RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc; RasterizerDesc.FillMode = FILL_MODE_SOLID; RasterizerDesc.CullMode = CULL_MODE_NONE; RasterizerDesc.FrontCounterClockwise = True; RasterizerDesc.ScissorEnable = True; RasterizerDesc.AntialiasedLineEnable = False; Depth-stencil and blend states are defined in a similar fashion.
Another important thing that pipeline state object encompasses is the input layout description that defines how inputs to the vertex shader, which is the very first shader stage, should be read from the memory. Input layout may define several vertex streams that contain values of different formats and sizes:
// Define input layout InputLayoutDesc &Layout = PSODesc.GraphicsPipeline.InputLayout; LayoutElement TextLayoutElems[] = {     LayoutElement( 0, 0, 3, VT_FLOAT32, False ),     LayoutElement( 1, 0, 4, VT_UINT8, True ),     LayoutElement( 2, 0, 2, VT_FLOAT32, False ), }; Layout.LayoutElements = TextLayoutElems; Layout.NumElements = _countof( TextLayoutElems ); Finally, pipeline state defines primitive topology type. When all required members are initialized, a pipeline state object can be created by IRenderDevice::CreatePipelineState() method:
// Define shader and primitive topology PSODesc.GraphicsPipeline.PrimitiveTopologyType = PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE; PSODesc.GraphicsPipeline.pVS = pVertexShader; PSODesc.GraphicsPipeline.pPS = pPixelShader; PSODesc.Name = "My pipeline state"; m_pDev->CreatePipelineState(PSODesc, &m_pPSO); When PSO object is bound to the pipeline, the engine invokes all API-specific commands to set all states specified by the object. In case of Direct3D12 this maps directly to setting the D3D12 PSO object. In case of Direct3D11, this involves setting individual state objects (such as rasterizer and blend states), shaders, input layout etc. In case of OpenGL, this requires a number of fine-grain state tweaking calls. Diligent Engine keeps track of currently bound states and only calls functions to update these states that have actually changed.
Binding Shader Resources
Direct3D11 and OpenGL utilize fine-grain resource binding models, where an application binds individual buffers and textures to certain shader or program resource binding slots. Direct3D12 uses a very different approach, where resource descriptors are grouped into tables, and an application can bind all resources in the table at once by setting the table in the command list. Resource binding model in Diligent Engine is designed to leverage this new method. It introduces a new object called shader resource binding that encapsulates all resource bindings required for all shaders in a certain pipeline state. It also introduces the classification of shader variables based on the frequency of expected change that helps the engine group them into tables under the hood:
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. Shader variable type must be specified during shader creation by populating an array of ShaderVariableDesc structures and initializing ShaderCreationAttribs::Desc::VariableDesc and ShaderCreationAttribs::Desc::NumVariables members (see example of shader creation above).
Static variables cannot be changed once a resource is bound to the variable. They are bound directly to the shader object. For instance, a shadow map texture is not expected to change after it is created, so it can be bound directly to the shader:
PixelShader->GetShaderVariable( "g_tex2DShadowMap" )->Set( pShadowMapSRV ); Mutable and dynamic variables are bound via a new Shader Resource Binding object (SRB) that is created by the pipeline state (IPipelineState::CreateShaderResourceBinding()):
m_pPSO->CreateShaderResourceBinding(&m_pSRB); Note that an SRB is only compatible with the pipeline state it was created from. SRB object inherits all static bindings from shaders in the pipeline, but is not allowed to change them.
Mutable resources can only be set once for every instance of a shader resource binding. Such resources are intended to define specific material properties. For instance, a diffuse texture for a specific material is not expected to change once the material is defined and can be set right after the SRB object has been created:
m_pSRB->GetVariable(SHADER_TYPE_PIXEL, "tex2DDiffuse")->Set(pDiffuseTexSRV); In some cases it is necessary to bind a new resource to a variable every time a draw command is invoked. Such variables should be labeled as dynamic, which will allow setting them multiple times through the same SRB object:
m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB); Under the hood, the engine pre-allocates descriptor tables for static and mutable resources when an SRB objcet is created. Space for dynamic resources is dynamically allocated at run time. Static and mutable resources are thus more efficient and should be used whenever possible.
As you can see, Diligent Engine does not expose low-level details of how resources are bound to shader variables. One reason for this is that these details are very different for various APIs. The other reason is that using low-level binding methods is extremely error-prone: it is very easy to forget to bind some resource, or bind incorrect resource such as bind a buffer to the variable that is in fact a texture, especially during shader development when everything changes fast. Diligent Engine instead relies on shader reflection system to automatically query the list of all shader variables. Grouping variables based on three types mentioned above allows the engine to create optimized layout and take heavy lifting of matching resources to API-specific resource location, register or descriptor in the table.
This post gives more details about the resource binding model in Diligent Engine.
Setting the Pipeline State and Committing Shader Resources
Before any draw or compute command can be invoked, the pipeline state needs to be bound to the context:
m_pContext->SetPipelineState(m_pPSO); Under the hood, the engine sets the internal PSO object in the command list or calls all the required native API functions to properly configure all pipeline stages.
The next step is to bind all required shader resources to the GPU pipeline, which is accomplished by IDeviceContext::CommitShaderResources() method:
m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); The method takes a pointer to the shader resource binding object and makes all resources the object holds available for the shaders. In the case of D3D12, this only requires setting appropriate descriptor tables in the command list. For older APIs, this typically requires setting all resources individually.
Next-generation APIs require the application to track the state of every resource and explicitly inform the system about all state transitions. For instance, if a texture was used as render target before, while the next draw command is going to use it as shader resource, a transition barrier needs to be executed. Diligent Engine does the heavy lifting of state tracking.  When CommitShaderResources() method is called with COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES flag, the engine commits and transitions resources to correct states at the same time. Note that transitioning resources does introduce some overhead. The engine tracks state of every resource and it will not issue the barrier if the state is already correct. But checking resource state is an overhead that can sometimes be avoided. The engine provides IDeviceContext::TransitionShaderResources() method that only transitions resources:
m_pContext->TransitionShaderResources(m_pPSO, m_pSRB); In some scenarios it is more efficient to transition resources once and then only commit them.
Invoking Draw Command
The final step is to set states that are not part of the PSO, such as render targets, vertex and index buffers. Diligent Engine uses Direct3D11-syle API that is translated to other native API calls under the hood:
ITextureView *pRTVs[] = {m_pRTV}; m_pContext->SetRenderTargets(_countof( pRTVs ), pRTVs, m_pDSV); // Clear render target and depth buffer const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); m_pContext->ClearDepthStencil(nullptr, CLEAR_DEPTH_FLAG, 1.f); // 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); Different native APIs use various set of function to execute draw commands depending on command details (if the command is indexed, instanced or both, what offsets in the source buffers are used etc.). For instance, there are 5 draw commands in Direct3D11 and more than 9 commands in OpenGL with something like glDrawElementsInstancedBaseVertexBaseInstance not uncommon. Diligent Engine hides all details with single IDeviceContext::Draw() method that takes 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); For compute commands, there is IDeviceContext::DispatchCompute() method that takes DispatchComputeAttribs structure that defines compute grid dimension.
Source Code
Full engine source code is available on GitHub and is free to use. The repository contains tutorials, sample applications, asteroids performance benchmark and an example Unity project that uses Diligent Engine in native plugin.
Atmospheric scattering sample demonstrates how Diligent Engine can be used to implement various rendering tasks: loading textures from files, using complex shaders, rendering to multiple render targets, using compute shaders and unordered access views, etc.

Asteroids performance benchmark is based on this demo developed by Intel. It renders 50,000 unique textured asteroids and allows comparing performance of Direct3D11 and Direct3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

Finally, there is an example project that shows how Diligent Engine can be integrated with Unity.

Future Work
The engine is under active development. It currently supports Windows desktop, Universal Windows, Linux, Android, MacOS, and iOS platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and Metal backend is in the plan.

• Good Evening,
I want to make a 2D game which involves displaying some debug information. Especially for collision, enemy sights and so on ...
First of I was thinking about all those shapes which I need will need for debugging purposes: circles, rectangles, lines, polygons.
I am really stucked right now because of the fundamental question:
Where do I store my vertices positions for each line (object)? Currently I am not using a model matrix because I am using orthographic projection and set the final position within the VBO. That means that if I add a new line I would have to expand the "points" array and re-upload (recall glBufferData) it every time. The other method would be to use a model matrix and a fixed vbo for a line but it would be also messy to exactly create a line from (0,0) to (100,20) calculating the rotation and scale to make it fit.
If I proceed with option 1 "updating the array each frame" I was thinking of having 4 draw calls every frame for the lines vao, polygons vao and so on.
In addition to that I am planning to use some sort of ECS based architecture. So the other question would be:
Should I treat those debug objects as entities/components?
For me it would make sense to treat them as entities but that's creates a new issue with the previous array approach because it would have for example a transform and render component. A special render component for debug objects (no texture etc) ... For me the transform component is also just a matrix but how would I then define a line?
Treating them as components would'nt be a good idea in my eyes because then I would always need an entity. Well entity is just an id !? So maybe its a component?
Regards,
LifeArtist
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