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OpenGL Calculate depth of front sphere from back side

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Currently sitting on an issue which i can't solve due to my lack of mathematical knowledge.

Here is a picture i made which sums up what i'm trying to do:

depthissue.png

 

To put it simply:

I render spheres (simple 3D meshes) into the scene on a seperate FBO by using frontface culling (so that the backside is rendered. The red part of the sphere on the screenshot.)

Now, in the fragment shader i can access the depth value of the rendered pixel by using "gl_Fragcoord.z". Now what i want to do is to calculate the depth value of the front facing side of the sphere of the exact same pixel. (so that i have a min and max depth value in order to know what the start depth and end depth value of the sphere on the given pixel is.) I need those values for post processing purposes.

 

My attempt to solve this was:

  1.  pass the current vertex position into the fragment shader
  2. subtract the vertex position from the origin point (in view space) to retrieve a normal pointing from the origin to the backface point
  3. Mirror the z-component of this normal (as we are in view space)
  4. add the mirrored normal to the origin point which gives us the front facing (vertex) position of the sphere
  5. use this position to calculate the depth value like in an openGL depth buffer. (haven't done this properly.)

depthissue2.png

 

I may or may not have an error in my shader code. (Maybe the way i multiply matrices is wrong?)

Here is my current code (a bit messy but i tried to comment it.)

//-------------- Vertex Shader --------------------
#version 330

layout (location = 0) in vec3 position;
layout (location = 1) in vec3 normal;
layout (location = 2) in vec4 color;
layout (location = 3) in vec2 uv;
 
uniform mat4 uProjectionMatrix;
uniform mat4 uModelViewMatrix;

out vec4 oColor;
out vec2 vTexcoord;

out vec4 vFragWorldPos;
out vec4 vOriginWorldPos;
out mat4 vProjectionMatrix;

void main()
{
    oColor = color;
	vTexcoord = uv;

	//coordinates are in view space!
	vec4 tFragWorldPos = (uModelViewMatrix * vec4(position,1.0));
	vec4 tOriginWorldPos = (uModelViewMatrix * vec4(0.0,0.0,0.0,1.0));
	

	vFragWorldPos = (uModelViewMatrix * vec4(position,1.0));
	vOriginWorldPos = (uModelViewMatrix * vec4(0.0,0.0,0.0,1.0));
	
    gl_Position = uProjectionMatrix * uModelViewMatrix * vec4(position,1.0);
	
	//send projection matrix to the fragment shader
	vProjectionMatrix = uProjectionMatrix;
}
//---------------- Fragment Shader --------------
#version 330
 
in vec4 oColor;
in vec2 vTexcoord;
out vec4 outputF;
in vec4 gl_FragCoord;


uniform sampler2D sGeometryDepth;
in vec4 gl_FragCoord;

in vec4 vFragWorldPos;
in vec4 vOriginWorldPos;
in mat4 vProjectionMatrix;


 
void main()
{

	//get texture coordinates of the screenspace depthbuffer
	vec2 relativeTexCoord = vec2(gl_FragCoord.x,gl_FragCoord.y);
	relativeTexCoord = relativeTexCoord-0.5+1.0;
	relativeTexCoord.x = relativeTexCoord.x/1280.0;
	relativeTexCoord.y = relativeTexCoord.y/720.0;
	

	//depth
	float backDepth = gl_FragCoord.z;//back depth
	float geometryDepth = texture2D(sGeometryDepth,relativeTexCoord).r;//geometry depth
	
	
	//--------------- Calculation of front depth---------------
	
	//get distance from origin to the fragment (normal in viewspace)
	vec3 offsetNormal = (vFragWorldPos/vFragWorldPos.w).xyz-(vOriginWorldPos/vOriginWorldPos.w).xyz;
	
	//mirror depth normal (z)
	offsetNormal.z*=-1.0;
	
	//add normal to origin point in order to get the mirrored coordinate point of the sphere
	vec4 sphereMirrorPos = vOriginWorldPos;
	sphereMirrorPos.xyz += offsetNormal.xyz;
	
	//apply perspective calculation
	vec4 projectedMirrorPos = vProjectionMatrix * sphereMirrorPos;
	projectedMirrorPos/=projectedMirrorPos.w;
	
	
	
	//TODO: CALCULATE PROPERLY
	float frontDepth = projectedMirrorPos.z * 0.5 + 0.5; // no idea what do do here further

	
	//want to color only the pixels where the scene depth (provided by a screen space texture which is a depthbuffer of a different FBO)
	//is exactly in between the min/max depth values of the sphere
	if(backDepth>geometryDepth && frontDepth<geometryDepth){
		outputF = vec4(1.0,1.0,1.0,1.0);
	}else{
		discard;
	}
	
	
}

 

I suspect that maybe transforming the coordinates into viewspace in the vertex shader (and working with those coordinates) may be an issue. (No idea where/when to divide by "W" for example.) Also i'm currently stuck at the part where i have to calculate the depth values in the same range as the OpenGL depth buffer in order to compare them in the if statement shown at the end of the fragment shader.

Hints/help would be greatly appreciated. 

Edited by Lewa

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I nearly got it working.

But there still seems to be a minor error in the calculation of the mirrored depth value.

Here is the current fragment shader (vertex shader is the same as above:)

#version 330
 
in vec4 oColor;
in vec2 vTexcoord;
out vec4 outputF;
in vec4 gl_FragCoord;


uniform sampler2D sGeometryDepth;
in vec4 gl_FragCoord;

in vec4 vFragWorldPos;
in vec4 vOriginWorldPos;
in mat4 vProjectionMatrix;

float linearizeDepth(float depthVal,float zNear,float zFar)
{
  float n = zNear; // camera z near
  float f = zFar; // camera z far
  float z = depthVal;
  return (2.0 * n) / (f + n - z * (f - n));	
}

void main()
{
	float uZnear = 0.01;
	float uZfar = 500.0;


	//get texture coordinates of the screenspace depthbuffer
	vec2 relativeTexCoord = vec2(gl_FragCoord.x,gl_FragCoord.y);
	relativeTexCoord = relativeTexCoord-0.5+1.0;
	relativeTexCoord.x = relativeTexCoord.x/1280.0;
	relativeTexCoord.y = relativeTexCoord.y/720.0;
	
	
	//depth of the backfacing sphere pixels and of the level geometry (depth texture of different FBO)
	float backDepth = linearizeDepth(gl_FragCoord.z,uZnear,uZfar);//back depth
	float geometryDepth = linearizeDepth(texture2D(sGeometryDepth,relativeTexCoord).r,uZnear,uZfar);//geometry depth
	
    //Now we have to calculate the front depth

	//--------------- Calculation of front depth---------------
	
	//get distance from origin to the fragment (in viewspace)
	
	float depthDiff = (vFragWorldPos.z-vOriginWorldPos.z);
	
	//substract depth difference from origin point in order to get the mirrored coordinate point of the sphere
	vec4 sphereMirrorPos = vec4(vFragWorldPos.xy,vOriginWorldPos.z - depthDiff,vOriginWorldPos.w);

	//apply perspective calculation
	vec4 projectedMirrorPos = vProjectionMatrix * sphereMirrorPos;
	projectedMirrorPos/=projectedMirrorPos.w;
	
	
	//depth calculation
	float frontDepth = (projectedMirrorPos.z + 1.0) / 2.0;
	frontDepth = linearizeDepth(frontDepth,uZnear,uZfar);
	

	//want to color only the pixels where the scene depth (provided by a screen space texture which is a depthbuffer of a different FBO)
	//is exactly in between the min/max depth values of the sphere
	
	if(backDepth>geometryDepth && frontDepth<geometryDepth){
		outputF = vec4(1.0,1.0,1.0,1.0);
	}else{
		discard;
	}
	

	
}

 

I believe the issue is somewhere here:

float depthDiff = (vFragWorldPos.z-vOriginWorldPos.z);
	
//add normal to origin point in order to get the mirrored coordinate point of the sphere
vec4 sphereMirrorPos = vec4(vFragWorldPos.xy,vOriginWorldPos.z - depthDiff,vOriginWorldPos.w);

"vFragWorldPos" is the position of the current vertex in ModelviewSpace. "vOriginWorldPos" is the origin of the sphere in modelviewSpace.

I simply calculate the z difference of both points by substracting the z components of both vectors.

Then i reconstruct the mirrored vertex coordinate by using the xy coordiantes of "vFragWorldPos" while the z-coordinate is calculated by substracting the depthDifference from the origin z-coordinate.

 

The issue is that it doesn't seem to give correct results by doing so.

I tested if this reconstruction method by changing this line:

vec4 sphereMirrorPos = vec4(vFragWorldPos.xy,vOriginWorldPos.z - depthDiff,vOriginWorldPos.w);

to this:

vec4 sphereMirrorPos = vec4(vFragWorldPos.xy,vOriginWorldPos.z + depthDiff,vOriginWorldPos.w);

which effectively calculates the depth of the back side of the sphere which i then compared with the values of the depth buffer. They are exactly the same. (which is correct.) But substracting the depthDiff value doesn't yield correct results.

 

Is there something that i'm missing? Maybe the z coordinates of the vertices which were transformed to modelview space aren't linear?

 

Edited by Lewa

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This sounds like an XY problem to me. Try backing up a step or two and describe what you're trying to accomplish. I suspect someone on these forums will be able to suggest a different approach that might work better.

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I only looked over the code quickly, so apologies if I'm misunderstanding something.  But, assuming your description of how you're trying to go about solving this, and that you're doing all the math in view space as you said... then it wont work because negating the z value wont give you what you think it gives you.  It wont give you a point backwards along the line of sight.

You can solve this by getting the point of intersection between the line of sight to the pixel and the line from the sphere origin that intersects that line at a right angle.  Once you get this point (lets call it midPoint) you're basically home free as you can just use the pixel position and midPoint to get the point your looking for.

Here's some pseudo code:

vec3 pixelPos;	// position in view space of the pixel on the sphere back face.  Known.
vec3 spherePos;	// position in view space of sphere origin.  Known.

vec3 tempDir = CrossProduct(spherePos, pixelPos);	// vector pointing up/down from plane
tempDir = CrossProduct(pixelPos, tempDir);		// vector pointing from line-of-sight towards spherePos
tempDir = Normalize(tempDir);

float d = DotProduct(tempDir, spherePos);	// distance along the "right" vector towards the sphere origin

vec3 midPoint = spherePos - tempDir * d;	// midPoint = point midway from front to backface along ling-of-sight

vec3 frontFacePos = 2 * midPoint - pixelPos;	// the frontface view-space point you want

Of course this code doesnt check to see if pixelPos and spherePos are parallel.  You'll need to check for that and handle the situation accordingly.  But, I think this will give you what you want... a point backwards along the line of sight (in view-space) from the backface of the sphere towards the frontface.

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On 7.08.2017 at 11:51 AM, 0r0d said:

I only looked over the code quickly, so apologies if I'm misunderstanding something.  But, assuming your description of how you're trying to go about solving this, and that you're doing all the math in view space as you said... then it wont work because negating the z value wont give you what you think it gives you.  It wont give you a point backwards along the line of sight.

You can solve this by getting the point of intersection between the line of sight to the pixel and the line from the sphere origin that intersects that line at a right angle.  Once you get this point (lets call it midPoint) you're basically home free as you can just use the pixel position and midPoint to get the point your looking for.

Here's some pseudo code:


vec3 pixelPos;	// position in view space of the pixel on the sphere back face.  Known.
vec3 spherePos;	// position in view space of sphere origin.  Known.

vec3 tempDir = CrossProduct(spherePos, pixelPos);	// vector pointing up/down from plane
tempDir = CrossProduct(pixelPos, tempDir);		// vector pointing from line-of-sight towards spherePos
tempDir = Normalize(tempDir);

float d = DotProduct(tempDir, spherePos);	// distance along the "right" vector towards the sphere origin

vec3 midPoint = spherePos - tempDir * d;	// midPoint = point midway from front to backface along ling-of-sight

vec3 frontFacePos = 2 * midPoint - pixelPos;	// the frontface view-space point you want

Of course this code doesnt check to see if pixelPos and spherePos are parallel.  You'll need to check for that and handle the situation accordingly.  But, I think this will give you what you want... a point backwards along the line of sight (in view-space) from the backface of the sphere towards the frontface.

That is EXACTLY what i needed/what i was looking for. Thank you!

Although i'm having a hard time understanding why this formula works. (As i seem to misunderstand how the viewspace works.)

Quote

Of course this code doesnt check to see if pixelPos and spherePos are parallel.

What exactly do you mean with "parallel"? If they are axis aligned in view space?

Edited by Lewa

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6 hours ago, Lewa said:

That is EXACTLY what i needed/what i was looking for. Thank you!

Although i'm having a hard time understanding why this formula works. (As i seem to misunderstand how the viewspace works.)

What exactly do you mean with "parallel"? If they are axis aligned in view space?

Here's a diagram that might help:

Untitled-1.thumb.jpg.02ffe96245f5107f535fe1c5c9e6e9a2.jpg

I think the problem is that you're thinking that view space means the Z values point along the line of sight to the camera.  But, view space is just camera space.  So when you take the vector (=> pixelPos - spherePos) and then negate the Z component, you get the "incorrect midPoint" seen above.  

So what you need is to find the correct midPoint by first finding the "tempDir" in the image, which is found by first finding the vector normal to the plane and then doing a cross product to find this new vector which is orthogonal to both the plane normal and the line of sight vector.  Once you have that vector you easily get the midPoint and then easily the frontFacePos.

Does that make sense?

As far as why it matters to check if spherePos and pixelPos are parallel... if they are parallel (ie they both lie on the line from camera to spherePos) then the first 2 cross products will give you a 0 length vector, and then the normalize operation will cause a divide by 0.  So, you need to check if the pixelPos is parallel to spherePos, in which case the frontFacePos would just be

frontFacePos = 2 * spherePos - pixelPos;

 

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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 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. 
    • By Balma Alparisi
      i got error 1282 in my code.
      sf::ContextSettings settings; settings.majorVersion = 4; settings.minorVersion = 5; settings.attributeFlags = settings.Core; sf::Window window; window.create(sf::VideoMode(1600, 900), "Texture Unit Rectangle", sf::Style::Close, settings); window.setActive(true); window.setVerticalSyncEnabled(true); glewInit(); GLuint shaderProgram = createShaderProgram("FX/Rectangle.vss", "FX/Rectangle.fss"); float vertex[] = { -0.5f,0.5f,0.0f, 0.0f,0.0f, -0.5f,-0.5f,0.0f, 0.0f,1.0f, 0.5f,0.5f,0.0f, 1.0f,0.0f, 0.5,-0.5f,0.0f, 1.0f,1.0f, }; GLuint indices[] = { 0,1,2, 1,2,3, }; GLuint vao; glGenVertexArrays(1, &vao); glBindVertexArray(vao); GLuint vbo; glGenBuffers(1, &vbo); glBindBuffer(GL_ARRAY_BUFFER, vbo); glBufferData(GL_ARRAY_BUFFER, sizeof(vertex), vertex, GL_STATIC_DRAW); GLuint ebo; glGenBuffers(1, &ebo); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,GL_STATIC_DRAW); glVertexAttribPointer(0, 3, GL_FLOAT, false, sizeof(float) * 5, (void*)0); glEnableVertexAttribArray(0); glVertexAttribPointer(1, 2, GL_FLOAT, false, sizeof(float) * 5, (void*)(sizeof(float) * 3)); glEnableVertexAttribArray(1); GLuint texture[2]; glGenTextures(2, texture); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageOne = new sf::Image; bool isImageOneLoaded = imageOne->loadFromFile("Texture/container.jpg"); if (isImageOneLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageOne->getSize().x, imageOne->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageOne->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageOne; glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageTwo = new sf::Image; bool isImageTwoLoaded = imageTwo->loadFromFile("Texture/awesomeface.png"); if (isImageTwoLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageTwo->getSize().x, imageTwo->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageTwo->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageTwo; glUniform1i(glGetUniformLocation(shaderProgram, "inTextureOne"), 0); glUniform1i(glGetUniformLocation(shaderProgram, "inTextureTwo"), 1); GLenum error = glGetError(); std::cout << error << std::endl; sf::Event event; bool isRunning = true; while (isRunning) { while (window.pollEvent(event)) { if (event.type == event.Closed) { isRunning = false; } } glClear(GL_COLOR_BUFFER_BIT); if (isImageOneLoaded && isImageTwoLoaded) { glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glUseProgram(shaderProgram); } glBindVertexArray(vao); glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr); glBindVertexArray(0); window.display(); } glDeleteVertexArrays(1, &vao); glDeleteBuffers(1, &vbo); glDeleteBuffers(1, &ebo); glDeleteProgram(shaderProgram); glDeleteTextures(2,texture); return 0; } and this is the vertex shader
      #version 450 core layout(location=0) in vec3 inPos; layout(location=1) in vec2 inTexCoord; out vec2 TexCoord; void main() { gl_Position=vec4(inPos,1.0); TexCoord=inTexCoord; } and the fragment shader
      #version 450 core in vec2 TexCoord; uniform sampler2D inTextureOne; uniform sampler2D inTextureTwo; out vec4 FragmentColor; void main() { FragmentColor=mix(texture(inTextureOne,TexCoord),texture(inTextureTwo,TexCoord),0.2); } I was expecting awesomeface.png on top of container.jpg

    • By khawk
      We've just released all of the source code for the NeHe OpenGL lessons on our Github page at https://github.com/gamedev-net/nehe-opengl. code - 43 total platforms, configurations, and languages are included.
      Now operated by GameDev.net, NeHe is located at http://nehe.gamedev.net where it has been a valuable resource for developers wanting to learn OpenGL and graphics programming.

      View full story
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