# OpenGL Drawing lots of 2D boxes; should I batch the draw call, and what's the best way to do that?

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When batching draw calls, how does one handle different transform matrices (position/rotation) for each object? Does each object's transformation matrix have to be applied before the batch draw call?

Specifically, I'm using OpenGL ES 2.0 to draw lots of 2D boxes. I can draw each one individually just fine, but seeing as I'm targeting mobile platforms, I'm looking to try to squeeze as much performance out of this as I can. The boxes aren't textured; mostly I'm interested in minimizing draw calls to save CPU time. The more CPU time I save, the larger my physics simulation can be.

• If I draw a lot of boxes and want to batch the draw calls together into one call, does that require that I apply the transformation matrices of each object to its vertices before copying all the objects into a single buffer for drawing?
• When batches are drawn, how does one differentiate between each object being drawn (if it's possible)? Perhaps my understanding of batching is wrong, but the way I currently understand it is that you cannot differentiate between each object (because you just take the vertices of all the objects to draw and copy them all into one buffer, so it just looks like a whole bunch of vertices; also this would require using GL_TRIANGLES instead of GL_TRIANGLE_STRIP (unless degenerate triangles were inserted) so as to not connect two different objects with a stray triangle)
• If you had a bunch of 2D boxes to draw, each with its own position, rotation, and scaling, but all of the same color (and no textures), how would you (personally) draw them? As a follow up, what if each had its own color; does that change things?

I don't know a lot about drawing optimization techniques. I'm comfortable drawing things to the screen, but I'm not a fancy graphics programmer.

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you can:
1. position vertices so that you only need 1 (or 2) matrices to determine their position in space
basically, if you have no choice but to transform them each frame, you can use the animation approach:
use a dynamic VBO, and transform each vertex each frame, and render everything in one go
this is a reasonable approach in many cases

2. use several draw calls: use one matrix that you translate back and forth, draw a range of vertices at a time
glDrawArrays takes 3 parameters: type, first, and count
so you would use the first parameter, and start with 0, then jump to say 4, 8, 12, 16.. if you only draw 1 box at a time
this is very slow though, so if you can, draw 100 boxes at a time

i use both, since if you have alot of vertices it may not be in your best interest to transform all of them each frame
instead using a few extra calls on groups of vertices that belong together is better
but it depends on your data
i'm sure other people can name other solutions, but as long as your boxes don't move, you should be able to do one or the other without problem
Edited by Kaptein

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I don't have a lot of experience on mobile platforms, but shouldn't the glDraw*Instanced family of calls solve your problem? You have one VBO containing the box geometry. In your shader you then have something like this
 #define MAX_INSTANCE SomeReasonableValue uniform mat4 mvp[MAX_INSTANCES]; ... outVertex = mvp[gl_InstanceID] * inVertex; 
The only bottleneck (that is, the number of glDraw*Instanced calls required to draw N boxes) there will be how much space you have for uniforms. If you are limited to certain kinds of transformations (for example only translations, uniform scale and/or rotations around one axis) for the boxes you could try to send only those parameters to the program and building an instance-specific matrix on the fly. Of course building that matrix for every vertex might well be more costly than setting the larger uniform matrices. However, if you are limited to translations only this could be better:
 uniform mat4 mvp; uniform vec3 translations[MAX_INSTANCES]; ... outVertex = mvp * (inVertex + vec4(translations[gl_InstanceID], 0));  Edited by BitMaster

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you can:
1. position vertices so that you only need 1 (or 2) matrices to determine their position in space
basically, if you have no choice but to transform them each frame, you can use the animation approach:
use a dynamic VBO, and transform each vertex each frame, and render everything in one go
this is a reasonable approach in many cases

That's one option I'm considering.

2. use several draw calls: use one matrix that you translate back and forth, draw a range of vertices at a time
glDrawArrays takes 3 parameters: type, first, and count
so you would use the first parameter, and start with 0, then jump to say 4, 8, 12, 16.. if you only draw 1 box at a time
this is very slow though, so if you can, draw 100 boxes at a time

Well, each box has its own transformation matrix because they're all independently movable, so I'm guessing this would require drawing one box at a time (using this method)?

i'm sure other people can name other solutions, but as long as your boxes don't move, you should be able to do one or the other without problem

The boxes certainly move, as they're part of a physics simulation, which unfortunately is what makes this complicated.

I don't have a lot of experience on mobile platforms, but shouldn't the glDraw*Instanced family of calls solve your problem?

I can certainly draw with them, but I'm trying to find ways to a) minimize the number of draw calls and b) put as much of the computation on the GPU instead of the CPU. I don't know how to draw things in batches without first applying each object's transformation matrix to all of its vertices on the CPU, and then using the transformed data in the draw call. I don't know if there's a different/better way to do this, because right now the options I'm seeing are a) make a draw call for each object and don't apply the transformations on the CPU, or b) apply the transformations on the CPU and make a batched draw call. I'm debating between the two and am interested if a third option exists.

You have one VBO containing the box geometry. In your shader you then have something like this
 #define MAX_INSTANCE SomeReasonableValue uniform mat4 mvp[MAX_INSTANCES]; ... outVertex = mvp[gl_InstanceID] * inVertex; 

That's a neat idea, but glDraw*Instanced() drawing didn't appear until OpenGL ES 3.0, and I'm stuck with 2.0

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For GLES 2.0 you have no choice but to do the transformation on CPU and load a dynamic VBO each frame if you have dynamic objects you want to batch.

On the plus-side, you have less calculations in your shader and can use that extra performance for making the pixels prettier. (or draw more boxes before GPU-limit) Edited by Olof Hedman

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What about adding N box geometries to the same VBO, just one after the other. For each geometry, add an additional integer attribute which is constant for each box (0 to N-1). Then you have basically a handrolled glDraw*Instanced in batches of maximal N, with your integer attribute taking the role of gl_InstanceID. Edited by BitMaster

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What about adding N box geometries to the same VBO, just one after the other. For each geometry, add an additional integer attribute which is constant for each box (0 to N-1). Then you have basically a handrolled glDraw*Instanced in batches of maximal N, with your integer attribute taking the role of gl_InstanceID.

You'd need to do add that attribute for each vertex, so a lot of extra integers.
I guess you'd have to put the matrixes in a texture too.
My gut says it will be slower then just transform on CPU, but I can't say I know Edited by Olof Hedman

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Hmm, I think I disregarded the case of 2D and only trivial shading.

If so, I guess more unorthodox methods could yield result, specially if the rest of the simulation tax the CPU.

The vertexes on a 2D box is less data then a matrix though, so I still say an efficient CPU-transform is probably the best

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Well, that will largely depend on exactly which transformations are needed. In the pure 2D case you can get away with a mat2x3 and still be completely general. For translation with rotation you can get away with a single vec3 (2D translation and angle) or maybe a vec4 (2D translation and precalculated sin(angle) and cos(angle)). I guess the 'best' solution to this problem will be extremely domain-specific, so the more ideas Cornstalks has lying around, the better. Edited by BitMaster

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The one recommendation I haven't seen is to consider jumping up to ES3. Now, that may not be viable for you, but if it is you'll have instancing support, so happy days - you're in the promised land.

If you can't do that then you've got a balancing act between the cost of splitting batches versus the cost of updating your vertex data in a manner that would allow you to take it all in a single batch.

For a desktop implementation without either instancing or glMapBufferRange (which would be required to update VBOs in a reasonable manner and without stalling the pipeline - again, ES3 would make that problem go away too) my gut inclination would be to drop the use of VBOs altogether, use client-side arrays in system memory, and transform on the CPU. Note that I said "desktop" here; I'm not certain how much of the following is going to apply to a mobile implementation so take it with the appropriate sized grain of salt.

Before proceeding it needs to be noted that ES2 does allow use of client-side arrays in this manner.

The main rationale behind this is that updating a VBO can be a horribly expensive operation - if you get it wrong it can be orders of magnitude more expensive than just not using VBOs at all. The reason why is that if the VBO is currently in use for drawing your program will not be able to immediately update it - instead it must stall, wait for all pending drawing operations to complete, then the update can happen. Do this a few too many times per frame and some implementations will plunge you to single digit framerates.

I'm guessing that you don't really want that to happen. ;)

So lets look at transforming a box on the CPU. This is not as horrible as it may appear at first glance.

First thing is to use indexed drawing (via glDrawElements) which will reduce the amount of vertices that need to be transformed from 24 to 8 - that's quite a significant saving already.

Second thing is to look at the transformation itself. There are several shortcuts you can take here, with an obvious one being to check if the box needs to be rotated - if it doesn't then the transformation collapses from a full set of matrix calculation/multiplies to 3 additions. Nice! The same applies to scaling; again you can collapse the full transform to something much much simpler (and faster).

One other factor here is that the indices used for drawing many boxes are going to be static - they'll never change, so you can just set them up once and reuse them as needed. You'll need to burn a bit of extra memory to set up indices for multiple boxes, but I believe that the tradeoff is worth it.

You could also get a further reduction in vertex submission by just not bothering to draw cube faces that are facing away from the viewpoint, but that would mess things up a little with your static indices (although you could work around it by collapsing them to 0-area triangles and reusing the same vertex for all of them). I'd maybe save that one for a later avenue of potential optimization if needed.

If my advice about VBOs turns out to be wrong on mobile platforms (i.e. if the cost of updating is lower than I estimate) then you're in a nice position where you can use a dynamic VBO, a static index buffer, and just fill/draw. I'm not sure if I'd be happy mixing client-side vertex data with an index buffer though, but my limited experience of mobile platforms measn that I can't really comment further on that one.

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Yeah, the best option will likely be very specific to my case. Specifically, this is a 2D game on Android where I'm using Box2D to simulate physical interactions of a large number of 2D boxes/rectangles. The boxes are not textured, and at the moment I'm considering making them all one color. The boxes can freely move and rotate during the simulation. Box2D gives me a translation vector (x and y) and rotation vector (precomputed sin and cos) for each box, and I know each box's size (I'm considering making them all the same size).

The one recommendation I haven't seen is to consider jumping up to ES3. Now, that may not be viable for you, but if it is you'll have instancing support, so happy days - you're in the promised land.

Unfortunately, I can't, as I'm targeting Android devices and the best thing available is ES2.0.

First thing is to use indexed drawing (via glDrawElements) which will reduce the amount of vertices that need to be transformed from 24 to 8 - that's quite a significant saving already.

These are 2D boxes, so the savings are significantly reduced (but still present). Are the savings still significant enough, do you think?

One thought I've had (there's a problem with it though) is to make one buffer that holds transformation matrices (really just vec4s representing the object's translation and rotation vectors) for every object, and then when drawing use an index array to index into the transformation matrix buffer. That way, each vertex can reference the corresponding box's transformation matrix and the box's transformation matrix only needs to be sent once. Each update would require updating the transformation matrix buffer. The problem, however, is another vertex buffer would be needed to define the 4 vertices for each box. This other vertex buffer only needs 4 elements, as all the boxes can be represented with the same vertices and a different transformation matrix. However, I don't think I can specify two index buffers, one which indexes into the transformation matrix buffer and the other which indexes into the little vertex buffer.

I'm seriously considering abandoning batching altogether at this point and just drawing each box individually (and transforming on the GPU using a uniform matrix passed in). Vertex data and buffer indices remain the same for each draw call. The only thing that would change is the uniform matrix. Thoughts?

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Hmmm - when I saw the word "box" I automatically assumed a 3D shape (even if projected onto a 2D view), but could you clarify - are you talking "boxes" as I assumed with 6 sides, 8 corners, or are you talking rectangles? I'd withdraw a huge chunk of my previous post if the latter (and happily accept negative rep on it too).

I'm seriously considering abandoning batching altogether at this point and just drawing each box individually (and transforming on the GPU using a uniform matrix passed in). Vertex data and buffer indices remain the same for each draw call. The only thing that would change is the uniform matrix. Thoughts?

Worth benchmarking and seeing how you go. It's incredibly simple to implement and may turn out to be not a problem at all. Edited by mhagain

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Hmmm - when I saw the word "box" I automatically assumed a 3D shape (even if projected onto a 2D view), but could you clarify - are you talking "boxes" as I assumed with 6 sides, 8 corners, or are you talking rectangles? I'd withdraw a huge chunk of my previous post if the latter (and happily accept negative rep on it too).

Boxes as in 2D rectangles and squares. 4 vertices, 2 triangles. I voted you up because even though a good amount of what you were talking about doesn't really apply in my particular case, there are things that you mentioned that I do appreciate because they may be very helpful in future projects.

I've got some basic rendering working now using the method in my last paragraph of my previous post. I plan on doing some stress testing and benchmarking and seeing if the rendering is enough of a bottleneck to try to optimize more, though I'm doubting it will at this point.

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• ### Similar Content

• By EddieK
Hello. I'm trying to make an android game and I have come across a problem. I want to draw different map layers at different Z depths so that some of the tiles are drawn above the player while others are drawn under him. But there's an issue where the pixels with alpha drawn above the player. This is the code i'm using:
int setup(){ GLES20.glEnable(GLES20.GL_DEPTH_TEST); GLES20.glEnable(GL10.GL_ALPHA_TEST); GLES20.glEnable(GLES20.GL_TEXTURE_2D); } int render(){ GLES20.glClearColor(0, 0, 0, 0); GLES20.glClear(GLES20.GL_ALPHA_BITS); GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT); GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT); GLES20.glBlendFunc(GLES20.GL_ONE, GL10.GL_ONE_MINUS_SRC_ALPHA); // do the binding of textures and drawing vertices } My vertex shader:
uniform mat4 MVPMatrix; // model-view-projection matrix uniform mat4 projectionMatrix; attribute vec4 position; attribute vec2 textureCoords; attribute vec4 color; attribute vec3 normal; varying vec4 outColor; varying vec2 outTexCoords; varying vec3 outNormal; void main() { outNormal = normal; outTexCoords = textureCoords; outColor = color; gl_Position = MVPMatrix * position; } My fragment shader:
precision highp float; uniform sampler2D texture; varying vec4 outColor; varying vec2 outTexCoords; varying vec3 outNormal; void main() { vec4 color = texture2D(texture, outTexCoords) * outColor; gl_FragColor = vec4(color.r,color.g,color.b,color.a);//color.a); } I have attached a picture of how it looks. You can see the black squares near the tree. These squares should be transparent as they are in the png image:

Its strange that in this picture instead of alpha or just black color it displays the grass texture beneath the player and the tree:

Any ideas on how to fix this?

• This article uses material originally posted on Diligent Graphics web site.
Introduction
Graphics APIs have come a long way from small set of basic commands allowing limited control of configurable stages of early 3D accelerators to very low-level programming interfaces exposing almost every aspect of the underlying graphics hardware. Next-generation APIs, Direct3D12 by Microsoft and Vulkan by Khronos are relatively new and have only started getting widespread adoption and support from hardware vendors, while Direct3D11 and OpenGL are still considered industry standard. New APIs can provide substantial performance and functional improvements, but may not be supported by older hardware. An application targeting wide range of platforms needs to support Direct3D11 and OpenGL. New APIs will not give any advantage when used with old paradigms. It is totally possible to add Direct3D12 support to an existing renderer by implementing Direct3D11 interface through Direct3D12, but this will give zero benefits. Instead, new approaches and rendering architectures that leverage flexibility provided by the next-generation APIs are expected to be developed.
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:
Lightweight abstractions: the API should be as close to the underlying native APIs as possible to allow an application leverage all available low-level functionality. In many cases this requirement is difficult to achieve because specific features exposed by different APIs may vary considerably. Low performance overhead: the abstraction layer needs to be efficient from performance point of view. If it introduces considerable amount of overhead, there is no point in using it. Convenience: the API needs to be convenient to use. It needs to assist developers in achieving their goals not limiting their control of the graphics hardware. Multithreading: ability to efficiently parallelize work is in the core of Direct3D12 and Vulkan and one of the main selling points of the new APIs. Support for multithreading in a cross-platform layer is a must. Extensibility: no matter how well the API is designed, it still introduces some level of abstraction. In some cases the most efficient way to implement certain functionality is to directly use native API. The abstraction layer needs to provide seamless interoperability with the underlying native APIs to provide a way for the app to add features that may be missing. Diligent Engine is designed to solve these problems. 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 C++ front-end for all supported platforms and provides interoperability with underlying native APIs. It also supports integration with Unity and is designed to be used as graphics subsystem in a standalone game engine, Unity native plugin or any other 3D application. Full source code is available for download at GitHub and is free to use.
Overview
Diligent Engine API takes some features from Direct3D11 and Direct3D12 as well as introduces new concepts to hide certain platform-specific details and make the system easy to use. It contains the following main components:
Render device (IRenderDevice  interface) is responsible for creating all other objects (textures, buffers, shaders, pipeline states, etc.).
Device context (IDeviceContext interface) is the main interface for recording rendering commands. Similar to Direct3D11, there are immediate context and deferred contexts (which in Direct3D11 implementation map directly to the corresponding context types). Immediate context combines command queue and command list recording functionality. It records commands and submits the command list for execution when it contains sufficient number of commands. Deferred contexts are designed to only record command lists that can be submitted for execution through the immediate context.
An alternative way to design the API would be to expose command queue and command lists directly. This approach however does not map well to Direct3D11 and OpenGL. Besides, some functionality (such as dynamic descriptor allocation) can be much more efficiently implemented when it is known that a command list is recorded by a certain deferred context from some thread.
The approach taken in the engine does not limit scalability as the application is expected to create one deferred context per thread, and internally every deferred context records a command list in lock-free fashion. At the same time this approach maps well to older APIs.
In current implementation, only one immediate context that uses default graphics command queue is created. To support multiple GPUs or multiple command queue types (compute, copy, etc.), it is natural to have one immediate contexts per queue. Cross-context synchronization utilities will be necessary.
Swap Chain (ISwapChain interface). Swap chain interface represents a chain of back buffers and is responsible for showing the final rendered image on the screen.
Render device, device contexts and swap chain are created during the engine initialization.
Resources (ITexture and IBuffer interfaces). There are two types of resources - textures and buffers. There are many different texture types (2D textures, 3D textures, texture array, cubmepas, etc.) that can all be represented by ITexture interface.
Resources Views (ITextureView and IBufferView interfaces). While textures and buffers are mere data containers, texture views and buffer views describe how the data should be interpreted. For instance, a 2D texture can be used as a render target for rendering commands or as a shader resource.
Pipeline State (IPipelineState interface). GPU pipeline contains many configurable stages (depth-stencil, rasterizer and blend states, different shader stage, etc.). Direct3D11 uses coarse-grain objects to set all stage parameters at once (for instance, a rasterizer object encompasses all rasterizer attributes), while OpenGL contains myriad functions to fine-grain control every individual attribute of every stage. Both methods do not map very well to modern graphics hardware that combines all states into one monolithic state under the hood. Direct3D12 directly exposes pipeline state object in the API, and Diligent Engine uses the same approach.
Shader Resource Binding (IShaderResourceBinding interface). Shaders are programs that run on the GPU. Shaders may access various resources (textures and buffers), and setting correspondence between shader variables and actual resources is called resource binding. Resource binding implementation varies considerably between different API. Diligent Engine introduces a new object called shader resource binding that encompasses all resources needed by all shaders in a certain pipeline state.
API Basics
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. Graphics APIs usually have a native object that represents linear buffer. Diligent Engine uses IBuffer interface as an abstraction for a native buffer. To create a buffer, one needs to populate BufferDesc structure and call IRenderDevice::CreateBuffer() method as in the following example:
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 ); While there is usually just one buffer object, different APIs use very different approaches to represent textures. For instance, in Direct3D11, there are ID3D11Texture1D, ID3D11Texture2D, and ID3D11Texture3D objects. In OpenGL, there is individual object for every texture dimension (1D, 2D, 3D, Cube), which may be a texture array, which may also be multisampled (i.e. GL_TEXTURE_2D_MULTISAMPLE_ARRAY). As a result there are nine different GL texture types that Diligent Engine may create under the hood. In Direct3D12, there is only one resource interface. Diligent Engine hides all these details in ITexture interface. There is only one  IRenderDevice::CreateTexture() method that is capable of creating all texture types. Dimension, format, array size and all other parameters are specified by the members of the TextureDesc structure:
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 ); If native API supports multithreaded resource creation, textures and buffers can be created by multiple threads simultaneously.
Interoperability with native API provides access to the native buffer/texture objects and also allows creating Diligent Engine objects from native handles. It allows applications seamlessly integrate native API-specific code with Diligent Engine.
Next-generation APIs allow fine level-control over how resources are allocated. Diligent Engine does not currently expose this functionality, but it can be added by implementing IResourceAllocator interface that encapsulates specifics of resource allocation and providing this interface to CreateBuffer() or CreateTexture() methods. If null is provided, default allocator should be used.
Initializing the Pipeline State
As it was mentioned earlier, Diligent Engine follows next-gen APIs 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.). This approach maps directly to Direct3D12/Vulkan, but is also beneficial for older APIs as it eliminates pipeline misconfiguration errors. With many individual calls tweaking various GPU pipeline settings it is very easy to forget to set one of the states or assume the stage is already properly configured when in fact it is not. Using pipeline state object helps avoid these problems as all stages are configured at once.
While in earlier APIs shaders were bound separately, in the next-generation APIs as well as in Diligent Engine shaders are part of the pipeline state object. The biggest challenge when authoring shaders is that Direct3D and OpenGL/Vulkan use different shader languages (while Apple uses yet another language in their Metal API). Maintaining two versions of every shader is not an option for real applications and Diligent Engine implements shader source code converter that allows shaders authored in HLSL to be translated to GLSL. To create a shader, one needs to populate ShaderCreationAttribs structure. SourceLanguage member of this structure tells the system which language the shader is authored in:
When sampling a texture in a shader, the texture sampler was traditionally specified as separate object that was bound to the pipeline at run time or set as part of the texture object itself. However, in most cases it is known beforehand what kind of sampler will be used in the shader. Next-generation APIs expose new type of sampler called static sampler that can be initialized directly in the pipeline state. Diligent Engine exposes this functionality: when creating a shader, textures can be assigned static samplers. If static sampler is assigned, it will always be used instead of the one initialized in the texture shader resource view. To initialize static samplers, prepare an array of StaticSamplerDesc structures and initialize StaticSamplers and NumStaticSamplers members. Static samplers are more efficient and it is highly recommended to use them whenever possible. On older APIs, static samplers are emulated via generic sampler objects.
The following is an example of shader initialization:
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.
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:
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 two samples, asteroids performance benchmark and example Unity project that uses Diligent Engine in native plugin.
AntTweakBar sample is Diligent Engine’s “Hello World” example.

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 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 and Android platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and support for more platforms is planned.
• By reenigne
For those that don't know me. I am the individual who's two videos are listed here under setup for https://wiki.libsdl.org/Tutorials
I also run grhmedia.com where I host the projects and code for the tutorials I have online.
Recently, I received a notice from youtube they will be implementing their new policy in protecting video content as of which I won't be monetized till I meat there required number of viewers and views each month.

Frankly, I'm pretty sick of youtube. I put up a video and someone else learns from it and puts up another video and because of the way youtube does their placement they end up with more views.
Even guys that clearly post false information such as one individual who said GLEW 2.0 was broken because he didn't know how to compile it. He in short didn't know how to modify the script he used because he didn't understand make files and how the requirements of the compiler and library changes needed some different flags.

At the end of the month when they implement this I will take down the content and host on my own server purely and it will be a paid system and or patreon.

I get my videos may be a bit dry, I generally figure people are there to learn how to do something and I rather not waste their time.
I used to also help people for free even those coming from the other videos. That won't be the case any more. I used to just take anyone emails and work with them my email is posted on the site.

I don't expect to get the required number of subscribers in that time or increased views. Even if I did well it wouldn't take care of each reoccurring month.
I figure this is simpler and I don't plan on putting some sort of exorbitant fee for a monthly subscription or the like.
I was thinking on the lines of a few dollars 1,2, and 3 and the larger subscription gets you assistance with the content in the tutorials if needed that month.
Maybe another fee if it is related but not directly in the content.
The fees would serve to cut down on the number of people who ask for help and maybe encourage some of the people to actually pay attention to what is said rather than do their own thing. That actually turns out to be 90% of the issues. I spent 6 hours helping one individual last week I must have asked him 20 times did you do exactly like I said in the video even pointed directly to the section. When he finally sent me a copy of the what he entered I knew then and there he had not. I circled it and I pointed out that wasn't what I said to do in the video. I didn't tell him what was wrong and how I knew that way he would go back and actually follow what it said to do. He then reported it worked. Yea, no kidding following directions works. But hey isn't alone and well its part of the learning process.

So the point of this isn't to be a gripe session. I'm just looking for a bit of feed back. Do you think the fees are unreasonable?
Should I keep the youtube channel and do just the fees with patreon or do you think locking the content to my site and require a subscription is an idea.

I'm just looking at the fact it is unrealistic to think youtube/google will actually get stuff right or that youtube viewers will actually bother to start looking for more accurate videos.

• i got error 1282 in my code.