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OpenGL Lighting (screens inside)...

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Hello everybody, this thread actually started in the Maths area, because I was sure, that my problem with lighting in OpenGL comes from some wrong normal calculation, but it seems like that is not the case. Thus I continue the thread here. I load objects as .3ds models into my application. I already checked the CW or CCW orientation of the triangles, but it turned out that they are consistent. I calculate the normals from my model data ( which is also correct, since I use the same data to actually draw my models ) and then I try to add lighting ( ambient, diffuse and specular for now ). My light is initially at position 0, 0, 0. When it is there, everything looks fine. The correct faces are lit up or not lit up according to their position/orientation. This is how it looks when the light is at the origin and everything is fine ( the light is at the origin of the particle system ). Now when I move my light in any direction, the faces start to flicker and sometimes wrong faces are lit up etc. Actually pretty much all the lighting messes up big time. This is how it looks when the lighting is messed up. And when I move the light even further away from the origin, the whole diffuse color ( which is the light component that messes up by the way ) disappears, and everything is lit only using the ambient color. So, this is how it looks now. I don't know what could be causing this problem. Here are the relevant code parts: Part of my initialization code...
	// enable texture mapping
	glEnable ( GL_TEXTURE_2D );

	// enable smooth shading
	glShadeModel ( GL_SMOOTH );

	// enable lighting
	glEnable ( GL_LIGHTING );

	// enable normalizing
	glEnable ( GL_NORMALIZE );

	glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
	glEnable(GL_COLOR_MATERIAL);

	// set background color
	glClearColor ( 0.6f, 0.6f, 0.6f, 1.0f );

	// depth buffer setup
	glClearDepth ( 1.0f );

	// initialize a light
	float ambient[] = { 0.0f, 0.0f, 0.0f, 1.0f };
	float diffuse[] = { 1.0f, 0.0f, 0.0f, 1.0f };
	float specular[] = { 12.0f, 12.0f, 12.0f, 12.0f };
	lgt.init ( ambient, diffuse, specular );
	lgt.toggle ( true );
}


My complete object::draw ( ) function...
void object::draw ( )
// draws the object normally to the screen
{
	// reset the matrix
	glLoadIdentity ( );

	// position the camera
	cam.update ( );

	// update acceleration values
	update_position ( );

	// move and rotate to place the object
	glTranslatef ( position.x, position.y, position.z );
	glRotatef ( rotation.x, 1.0f, 0.0f, 0.0f );
	glRotatef ( rotation.y, 0.0f, 1.0f, 0.0f );
	glRotatef ( rotation.z, 0.0f, 0.0f, 1.0f );

	// set up render modes
	glColorMask ( 1, 1, 1, 1 );
	glColor4f ( 1.0f, 1.0f, 1.0f, 1.0f );
	glDisable ( GL_BLEND );
	glDisable ( GL_CLIP_PLANE0 );
	glEnable ( GL_DEPTH_TEST );
	glDisable ( GL_STENCIL_TEST );

	if ( sphere_mapped == true )
	// if the object is sphere mapped
	{
		// enable sphere mapping
		glEnable ( GL_TEXTURE_GEN_S );
		glEnable ( GL_TEXTURE_GEN_T );
	}
	else
	// if the object is texture mapped
	{
		// disable shere mapping
		glDisable ( GL_TEXTURE_GEN_S );
		glDisable ( GL_TEXTURE_GEN_T );
	}

	// activate texture
	surface_texture.activate ( );

	// push the matrix
	glPushMatrix ( );

	// scale
	glScalef ( size, size, size );

	for ( int i = 0; i < actor.num_polygons; i++ )
	// loop through each polygon
	{
		float vertex1[3], vertex2[3], vertex3[3];

		// prepare vertex data
		vertex1[0] = actor.vertex[actor.polygon.a ].x;
		vertex1[1] = actor.vertex[actor.polygon.a ].y;
		vertex1[2] = actor.vertex[actor.polygon.a ].z;
		vertex2[0] = actor.vertex[actor.polygon.b ].x;
		vertex2[1] = actor.vertex[actor.polygon.b ].y;
		vertex2[2] = actor.vertex[actor.polygon.b ].z;
		vertex3[0] = actor.vertex[actor.polygon.c ].x;
		vertex3[1] = actor.vertex[actor.polygon.c ].y;
		vertex3[2] = actor.vertex[actor.polygon.c ].z;
		
		// get the face normal
		get_face_normal ( actor.normal, vertex1, vertex2, vertex3 );

		// multiply it by -1
		actor.normal[0] *= -1;
		actor.normal[1] *= -1;
		actor.normal[2] *= -1;

		cgGLSetParameter3f ( vertexPosition, vertex1[0], vertex1[1], vertex1[2] );
		cgGLSetParameter3f ( vertexNormal, actor.normal[0], actor.normal[1], actor.normal[2] );

		// begin drawing polygon
		glBegin ( GL_TRIANGLES );
		
		// activate face normal
		glNormal3f ( actor.normal[0], actor.normal[1], actor.normal[2] );		

		// draw first vertex
		glTexCoord2f ( actor.mapcoord[actor.polygon.a].u, actor.mapcoord[actor.polygon.a].v );
		glVertex3f ( actor.vertex[actor.polygon.a ].x, actor.vertex[actor.polygon.a ].y, actor.vertex[actor.polygon.a ].z );
		
		// draw second vertex
		glTexCoord2f ( actor.mapcoord[actor.polygon.b].u, actor.mapcoord[actor.polygon.b].v );
		glVertex3f ( actor.vertex[actor.polygon.b].x, actor.vertex[actor.polygon.b].y, actor.vertex[actor.polygon.b].z );

		// draw third vertex
		glTexCoord2f ( actor.mapcoord[actor.polygon.c].u, actor.mapcoord[actor.polygon.c].v );
		glVertex3f ( actor.vertex[actor.polygon.c].x, actor.vertex[actor.polygon.c].y, actor.vertex[actor.polygon.c].z );

		// done drawing polygon
		glEnd ( );
    }

	// pop the matrix
	glPopMatrix ( );
		
	// disable sphere mapping
	glDisable ( GL_TEXTURE_GEN_S );
	glDisable ( GL_TEXTURE_GEN_T );
}


My light class definitions ( that I used in the initialization code above )...
void light::init ( float ambient[], float diffuse[], float specular[] )
// initializes a light
{
	glLightfv ( GL_LIGHT1, GL_AMBIENT, ambient );
	glLightfv ( GL_LIGHT1, GL_DIFFUSE, diffuse );
	glLightfv ( GL_LIGHT1, GL_SPECULAR, specular );
	glLightModeli ( GL_LIGHT_MODEL_TWO_SIDE, GL_TRUE );
	glEnable ( GL_LIGHT1 );
}

void light::toggle ( void )
// toggles a light on or off
{
	if ( mode == true )
	// if light is activated
	{
		glDisable ( GL_LIGHT1 );
		mode = false;
	}
	else
	// if light is deactivated
	{
		glEnable ( GL_LIGHT1 );
		mode = true;
	}
}

void light::toggle ( bool new_mode )
// switch a light to a specific state
{
	mode = new_mode;

	if ( mode == true )
	// if light is activated
		glEnable ( GL_LIGHT1 );
	else
	// if light is activated
		glDisable ( GL_LIGHT1 );
}


void light::set_position ( float light_position[] )
// updates the position of the light
{
	// reset the matrix
	glLoadIdentity ( );

	// position the camera
	cam.update ( );

	// move the light
	glLightfv ( GL_LIGHT1, GL_POSITION, light_position );
}



My normal calculations ( should be correct though )...
void cross_product ( float *c,float a[3], float b[3] )
// finds the cross product of two vectors
{  
	c[0] = a[1] * b[2] - b[1] * a[2];
	c[1] = a[2] * b[0] - b[2] * a[0];
	c[2] = a[0] * b[1] - b[0] * a[1];
}

void normalize ( float * vect )
// scales a vector to a length of 1
{
	float length;
	int a;

	length = ( float ) sqrt ( pow ( vect[0], 2 ) + pow ( vect[1], 2 ) + pow ( vect[2], 2 ) );

	for ( a = 0; a < 3; ++a )
	// divides vector by its length to normalize
	{
		vect[a] /= length;
	}
}

void get_face_normal ( float *norm, float pointa[3], float pointb[3], float pointc[3] )
// gets the normal of a face
{
	float vect[2][3];
	int a,b;
	float point[3][3];

	for ( a = 0; a < 3; ++a )
	// copies points into point[][]
	{
		point[0][a]=pointa[a];
		point[1][a]=pointb[a]; 
		point[2][a]=pointc[a];
	}

	for ( a = 0; a < 2; ++a )
	// calculates vectors from point[0] to point[1]
	{                       
		for ( b = 0; b < 3; ++b )
		// and point[0] to point[2]
		{
			vect[a] = point[2-a] - point[0];      
		}
	}

	// calculates vector at 90° to to 2 vectors
	cross_product ( norm, vect[0], vect[1] );

	// makes the vector length 1
	normalize ( norm );
}


Can anybody help me? What is wrong? [Edited by - d h k on October 8, 2005 9:01:30 AM]

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Sorry to bump this thread, but it was just about to slip away from the first page. And considering there where ~60 views and not one single reply, I suppose I didn't express my problem correct.

Is anything not clear to you or do you guys just don't have any idea of what could be wrong? I know I posted four sections of code, but they're not that long ( together maybe 100 lines maximum ).

Again I am sorry if I seem annoying with this problem, but I really need help for this. It's one of the last technical steps for this application.

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First off, I suggest you draw your normals to make sure they're correct. They probably are, but it pays to make sure you're debugging something thats actually broken. :) Simply drawing lines for every vertex between vertexPos and vertexPos+normal*scale (just tweek 'scale' until the lines are of sensible length) will let you instantly tell if they're correct or not.

However I think your problem is with your order of operations. For hardware lights you want to do:

- clear screen
- set projection matrix
- set camera position (in modelview matrix)
- enable/set lights
- for each object
-- push modelview matrix
-- position / rotate object via modelview
-- render object
-- pop modelview matrix

The key difference is that you seem to be setting the lights, then setting the camera, which is the wrong way of doing things. When lights are specified they are transformed using the current set of matrices into screen space. Instead do view and camera setup first, then lights.

Hope that helps.

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Thanks for your reply.

First of all I checked the normals and they look fine.

Then I tried to follow your advice, but it seems I still have problems with it. I guess since the problem is the order, the problem is in the global draw function, that determines the order:

This is the way I used to have this function set up:

void draw_world ( void )
// draws the world
{
// clear screen buffer, depth buffer and stencil buffer
glClear ( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT );

// reset the matrix
glLoadIdentity ( );

float lgt_pos[] = { prt_system.position.x, prt_system.position.y, prt_system.position.z };
lgt.set_position ( lgt_pos );

// draw the gui
draw_gui ( );

// and draw the map
map.draw ( );

// then draw the objects
draw_objects ( );
}



This is the new function, that I now use:

void draw_world ( void )
// draws the world
{
glClear ( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT );

glLoadIdentity ( );

glMatrixMode ( GL_PROJECTION );

glPushMatrix ( );

cam.update ( );

glPopMatrix ( );

glMatrixMode ( GL_MODELVIEW );

glPushMatrix ( );

float lgt_pos[] = { prt_system.position.x, prt_system.position.y, prt_system.position.z };
lgt.set_position ( lgt_pos );

draw_gui ( );
draw_objects ( );

glPopMatrix ( );
}



But it still looks the very same!

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In your new function, you have:
glMatrixMode ( GL_PROJECTION );
glPushMatrix ( );
cam.update ( );
glPopMatrix ( );
Assuming that cam.update sets the camera position, then that doesn't have any effect. You don't need any pushing or poping here (although a glIdentity before the camera might be a good idea).

You don't say what your new draw_objects() does. Make sure you're not still doing your object::draw in the same way - you don't want to set the camera at this point, it should already be set!

Your whole matrix setup looks convulted and error prone. You really should decide what should happen where and stick with it. It might be an idea to rip out what you've already got and add in bits slowly (following the order i listed before).

Edit: and you don't appear to be setting the camera's modelview matrix up anywhere (which should be *before* you setup lights).

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You are right, the whole function is quite messed up. I cleaned it up, but now it doesn't render anything anymore...

This is the new draw_world function (that draws everything):

void draw_world ( void )
// draws the world
{
// clear screen
glClear ( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT );

// set projection matrix
glMatrixMode ( GL_PROJECTION );

// reset
glLoadIdentity ( );

// move for camera
cam.update ( );

// set modelview matrix
glMatrixMode ( GL_MODELVIEW );

// set lights
float lgt_pos[] = { prt_system.position.x, prt_system.position.y, prt_system.position.z };
lgt.set_position ( lgt_pos );

// draw lights
draw_objects ( );
}




Then this is my draw_objects function (that draws objects):

void draw_objects ( void )
// draws all objects
{
obj[1].mask ( );

obj[0].draw_reflected ( );
obj[2].draw_reflected ( );
prt_system.draw_reflected ( );

obj[1].draw_blended ( );

obj[0].draw ( );
obj[2].draw ( );
prt_system.draw ( );
}




And finally this is my object::draw function (that really draws one object):

void object::draw ( )
// draws the object normally to the screen
{
// set up render modes
glColorMask ( 1, 1, 1, 1 );
glColor4f ( 1.0f, 1.0f, 1.0f, 1.0f );
glDisable ( GL_BLEND );
glDisable ( GL_CLIP_PLANE0 );
glEnable ( GL_DEPTH_TEST );
glDisable ( GL_STENCIL_TEST );

if ( sphere_mapped == true )
// if the object is sphere mapped
{
// enable sphere mapping
glEnable ( GL_TEXTURE_GEN_S );
glEnable ( GL_TEXTURE_GEN_T );
}
else
// if the object is texture mapped
{
// disable shere mapping
glDisable ( GL_TEXTURE_GEN_S );
glDisable ( GL_TEXTURE_GEN_T );
}

// activate texture
surface_texture.activate ( );

// push the matrix
glPushMatrix ( );

// move and rotate to place the object
glTranslatef ( position.x, position.y, position.z );
glRotatef ( rotation.x, 1.0f, 0.0f, 0.0f );
glRotatef ( rotation.y, 0.0f, 1.0f, 0.0f );
glRotatef ( rotation.z, 0.0f, 0.0f, 1.0f );

// scale
glScalef ( size, size, size );

for ( int i = 0; i < actor.num_polygons; i++ )
// loop through each polygon
{
float vertex1[3], vertex2[3], vertex3[3];

// prepare vertex data
vertex1[0] = actor.vertex[actor.polygon.a ].x;
vertex1[1] = actor.vertex[actor.polygon.a ].y;
vertex1[2] = actor.vertex[actor.polygon.a ].z;
vertex2[0] = actor.vertex[actor.polygon.b ].x;
vertex2[1] = actor.vertex[actor.polygon.b ].y;
vertex2[2] = actor.vertex[actor.polygon.b ].z;
vertex3[0] = actor.vertex[actor.polygon.c ].x;
vertex3[1] = actor.vertex[actor.polygon.c ].y;
vertex3[2] = actor.vertex[actor.polygon.c ].z;

// get the face normal
get_face_normal ( actor.normal, vertex1, vertex2, vertex3 );

// multiply it by -1
actor.normal[0] *= -1;
actor.normal[1] *= -1;
actor.normal[2] *= -1;

glBegin ( GL_LINES );

glVertex3f ( vertex1[0], vertex1[1], vertex1[2] );
glVertex3f ( vertex1[0]+actor.normal[0]*10.0f, vertex1[1]+actor.normal[1]*10.0f, vertex1[2]+actor.normal[2]*10.0f );

glVertex3f ( vertex2[0], vertex2[1], vertex2[2] );
glVertex3f ( vertex2[0]+actor.normal[0]*10.0f, vertex2[1]+actor.normal[1]*10.0f, vertex2[2]+actor.normal[2]*10.0f );

glVertex3f ( vertex3[0], vertex3[1], vertex3[2] );
glVertex3f ( vertex3[0]+actor.normal[0]*10.0f, vertex3[1]+actor.normal[1]*10.0f, vertex3[2]+actor.normal[2]*10.0f );

glEnd ( );

// begin drawing polygon
glBegin ( GL_TRIANGLES );

// activate face normal
glNormal3f ( actor.normal[0], actor.normal[1], actor.normal[2] );

// draw first vertex
glTexCoord2f ( actor.mapcoord[actor.polygon.a].u, actor.mapcoord[actor.polygon.a].v );
glVertex3f ( actor.vertex[actor.polygon.a ].x, actor.vertex[actor.polygon.a ].y, actor.vertex[actor.polygon.a ].z );

// draw second vertex
glTexCoord2f ( actor.mapcoord[actor.polygon.b].u, actor.mapcoord[actor.polygon.b].v );
glVertex3f ( actor.vertex[actor.polygon.b].x, actor.vertex[actor.polygon.b].y, actor.vertex[actor.polygon.b].z );

// draw third vertex
glTexCoord2f ( actor.mapcoord[actor.polygon.c].u, actor.mapcoord[actor.polygon.c].v );
glVertex3f ( actor.vertex[actor.polygon.c].x, actor.vertex[actor.polygon.c].y, actor.vertex[actor.polygon.c].z );

// done drawing polygon
glEnd ( );
}

// pop the matrix
glPopMatrix ( );

// disable sphere mapping
glDisable ( GL_TEXTURE_GEN_S );
glDisable ( GL_TEXTURE_GEN_T );
}




The only point I am missing on your list is the "setting-the-cameras-modelview-matrix-up", because I am not quite sure what you meant.

My camera::update function does this:

void camera::update ( void )
// updates the cameras position in the world
{
// move there
glTranslatef ( position.x, position.y, position.z );
glRotatef ( rotation.x, 1.0f, 0.0f, 0.0f );
glRotatef ( rotation.y, 0.0f, 1.0f, 0.0f );
glRotatef ( rotation.z, 0.0f, 0.0f, 1.0f );
}




Thanks for your help though, I already rated you up. (:

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That looks better, but I think your camera setup is wrong. You want your perspective setup on the projection matrix and your actual camera position on the modelview matrix. Basically something like:

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glPerspective( whatever settings );

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
// the stuff you've got in camera.update to set the position

// Rest of your drawing here. Looks ok now though :)

At the moment you're putting your camera orientation/position in the projection matrix, and you're not setting the projection matrix at all.

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Allright, now it renders again. And is like 12x faster, too. ;) Thanks for that!

Just the original problem is still the same. The lighting screws up whenever I move the light.

This is the new and corrected draw_world function:

void draw_world ( void )
// draws the world
{
// clear screen
glClear ( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT );

// set projection matrix
glMatrixMode ( GL_PROJECTION );

// reset
glLoadIdentity ( );

// perspective setup
gluPerspective ( 45.0f, (GLfloat)SCREEN_WIDTH / (GLfloat)SCREEN_HEIGHT, 0.1f, 800.0f );

// set modelview matrix
glMatrixMode ( GL_MODELVIEW );

// reset
glLoadIdentity ( );

// move for camera
cam.update ( );

// set lights
float lgt_pos[] = { prt_system.position.x, prt_system.position.y, prt_system.position.z };
lgt.set_position ( lgt_pos );

// draw objects
draw_objects ( );
}


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Is your light::set_position still the same as your first post? You really don't want to be messing with the camera and matrices in there. :)

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Yes, I'm afraid it is still the same...

Here for you to check (one line): ;)


void light::set_position ( float light_position[] )
// updates the position of the light
{
// move the light
glLightfv ( GL_LIGHT1, GL_POSITION, light_position );
}

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Where did you get that gun model? I'm interested in obtaining a low-poly assault rifle model (preferably an AK).

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I made it myself. First model I ever made. But its mesh is not optimized at all and usually I can't model for nothing. Look at www.turbosquid.com to find good models.

Anybody has any suggestions for the problem though? I really don't know what could be wrong. Once I moved the light (and once the lighting is all messed up) I can suddenly change the way it looks by moving / rotation the camera. If the light is at the origin when it all looks good, I can't (like I am supposed to). But I have no idea what could be causing this strange behaviour.

EDIT:

I am sorry for bumping this, but the thread was about to slip of the front page and I really need help here. I have no clue what could still be wrong! Please reply, even if you only say, you need more information or if there is something not clear to you. Any help is appreciated (sp?) big time.

Thanks

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1)In you camera setup code, you need to first do the rotation, and then the translation(using the negated position). Like this:


glRotatef (rotation.x, 1.0f, 0.0f, 0.0f );
glRotatef (rotation.y, 0.0f, 1.0f, 0.0f );
glRotatef (rotation.z, 0.0f, 0.0f, 1.0f );
glTranslatef (-position.x,-position.y,-position.z );




2)The light position must be a 4-element array, with the 4th element being 1 for positional and 0 for directional light(you need positional):

// set lights
float lgt_pos[] = { prt_system.position.x, prt_system.position.y, prt_system.position.z,1.0 };
lgt.set_position ( lgt_pos );


The way you do it now, you feed a 3-element array when glLightfv expects 4(x,y,z,w), so in the best case it will read garbage and in the worst it will crash.

Generally, I suggest you go back and make a good read of the Red Book, because you seem to be confused about a lot of basic things.

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Ah, that did it. Thanks a lot.

You are right, I'll take some time off to read the red book now. Should've done it earlier.

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      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.
      Creating Shaders
      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:
      SHADER_SOURCE_LANGUAGE_DEFAULT - The shader source language matches the underlying graphics API: HLSL for Direct3D11/Direct3D12 mode, and GLSL for OpenGL and OpenGLES modes. SHADER_SOURCE_LANGUAGE_HLSL - The shader source is in HLSL. For OpenGL and OpenGLES modes, the source code will be converted to GLSL. SHADER_SOURCE_LANGUAGE_GLSL - The shader source is in GLSL. There is currently no GLSL to HLSL converter, so this value should only be used for OpenGL and OpenGLES modes. There are two ways to provide the shader source code. The first way is to use Source member. The second way is to provide a file path in FilePath member. Since the engine is entirely decoupled from the platform and the host file system is platform-dependent, the structure exposes pShaderSourceStreamFactory member that is intended to provide the engine access to the file system. If FilePath is provided, shader source factory must also be provided. If the shader source contains any #include directives, the source stream factory will also be used to load these files. The engine provides default implementation for every supported platform that should be sufficient in most cases. Custom implementation can be provided when needed.
      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:
      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.
    • By LifeArtist
      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
    • By QQemka
      Hello. I am coding a small thingy in my spare time. All i want to achieve is to load a heightmap (as the lowest possible walking terrain), some static meshes (elements of the environment) and a dynamic character (meaning i can move, collide with heightmap/static meshes and hold a varying item in a hand ). Got a bunch of questions, or rather problems i can't find solution to myself. Nearly all are deal with graphics/gpu, not the coding part. My c++ is on high enough level.
      Let's go:
      Heightmap - i obviously want it to be textured, size is hardcoded to 256x256 squares. I can't have one huge texture stretched over entire terrain cause every pixel would be enormous. Thats why i decided to use 2 specified textures. First will be a tileset consisting of 16 square tiles (u v range from 0 to 0.25 for first tile and so on) and second a 256x256 buffer with 0-15 value representing index of the tile from tileset for every heigtmap square. Problem is, how do i blend the edges nicely and make some computationally cheap changes so its not obvious there are only 16 tiles? Is it possible to generate such terrain with some existing program?
      Collisions - i want to use bounding sphere and aabb. But should i store them for a model or entity instance? Meaning i have 20 same trees spawned using the same tree model, but every entity got its own transformation (position, scale etc). Storing collision component per instance grats faster access + is precalculated and transformed (takes additional memory, but who cares?), so i stick with this, right? What should i do if object is dynamically rotated? The aabb is no longer aligned and calculating per vertex min/max everytime object rotates/scales is pretty expensive, right?
      Drawing aabb - problem similar to above (storing aabb data per instance or model). This time in my opinion per model is enough since every instance also does not have own vertex buffer but uses the shared one (so 20 trees share reference to one tree model). So rendering aabb is about taking the model's aabb, transforming with instance matrix and voila. What about aabb vertex buffer (this is more of a cosmetic question, just curious, bumped onto it in time of writing this). Is it better to make it as 8 points and index buffer (12 lines), or only 2 vertices with min/max x/y/z and having the shaders dynamically generate 6 other vertices and draw the box? Or maybe there should be just ONE 1x1x1 cube box template moved/scaled per entity?
      What if one model got a diffuse texture and a normal map, and other has only diffuse? Should i pass some bool flag to shader with that info, or just assume that my game supports only diffuse maps without fancy stuff?
      There were several more but i forgot/solved them at time of writing
      Thanks in advance
    • By RenanRR
      Hi All,
      I'm reading the tutorials from learnOpengl site (nice site) and I'm having a question on the camera (https://learnopengl.com/Getting-started/Camera).
      I always saw the camera being manipulated with the lookat, but in tutorial I saw the camera being changed through the MVP arrays, which do not seem to be camera, but rather the scene that changes:
      Vertex Shader:
      #version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec2 aTexCoord; out vec2 TexCoord; uniform mat4 model; uniform mat4 view; uniform mat4 projection; void main() { gl_Position = projection * view * model * vec4(aPos, 1.0f); TexCoord = vec2(aTexCoord.x, aTexCoord.y); } then, the matrix manipulated:
      ..... glm::mat4 projection = glm::perspective(glm::radians(fov), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); ourShader.setMat4("projection", projection); .... glm::mat4 view = glm::lookAt(cameraPos, cameraPos + cameraFront, cameraUp); ourShader.setMat4("view", view); .... model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f)); ourShader.setMat4("model", model);  
      So, some doubts:
      - Why use it like that?
      - Is it okay to manipulate the camera that way?
      -in this way, are not the vertex's positions that changes instead of the camera?
      - I need to pass MVP to all shaders of object in my scenes ?
       
      What it seems, is that the camera stands still and the scenery that changes...
      it's right?
       
       
      Thank you
       
    • By dpadam450
      Sampling a floating point texture where the alpha channel holds 4-bytes of packed data into the float. I don't know how to cast the raw memory to treat it as an integer so I can perform bit-shifting operations.

      int rgbValue = int(textureSample.w);//4 bytes of data packed as color
      // algorithm might not be correct and endianness might need switching.
      vec3 extractedData = vec3(  rgbValue & 0xFF000000,  (rgbValue << 8) & 0xFF000000, (rgbValue << 16) & 0xFF000000);
      extractedData /= 255.0f;
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