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OpenGL Question about multiple Vertex Buffer...

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Hi, in opengl, when i load my models using vertex buffer, it's very easy to use only the buffers that i need for a particular model(ex. one model with texture and lighting, the other whithout lighting, the other one with fog, ect...), but in DX, i ran into the problem that you must define you're FVF yourself, so that make thing a little more complicated... How can i use multiple vertex buffer for one object efficietly? Thx for any help!

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When I need something like that I just have one model with all things I might possibly need(position, normals etc...) and then in vertex I use only things I need now.

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ok, but do you create multiple vertex buffers or use one big "interleaved"
buffer? I need to be able to use one or more of of the 6 following:

-Vertex positon
-Color
-Texture coord 1
-Texture coord 2
-Normals
-Fog

Im a beginner in dx but know opengl very well so i just need a simple example or something like that... Thx for ur time.

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hmm, I would use vertex declarations here. read about it in directX SDK documentation and here . I`m sure you can find more if you search on gamedev. and I use one big buffer. and even if I could have multiple small ones I don`t see any benefit. you just make vertex shader like

struct VS_OUTPUT
{
float4 pos :POSITION;
float2 tex :TEXCOORD0;
};

VS_OUTPUT basicVs(float4 pos :POSITION, float2 tex :TEXCOORD0)
{
VS_OUTPUT Output;
float4x4 projView = mul(view, projection);
Output.pos = mul(pos, projView);
Output.tex = tex;
return Output;
}


if you need only position and tex coords 1. if you needed normals, you would just add :NORMAL etc... notice that what you marked as position in vertex declaration is used as position here.

and for fog. you don`t need it in vertices(unless you are doing something special). in SDK there are several articles about it.

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Ok, seem to work perfectly for vertex position, color, and normals now,
i used vertex declaration and this time it work, some code was incomplete...

(In fact, im building the dx version of my opengl engine, so im trying
to make both version work in similar maners, then i'll merge them togeter when
the dx version will be more stable)

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I also want to know, is there is a way to tell dx to use white for example
on all mesh without passing a color buffer each time? I also noticed that
i might not need it when i use lighting, cause the color buffer seem to
have no effect in this case. So im not sure what to do...

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yeah, color on vertices is pretty useless when rendering textured meshes. or at least I can`t see any use for it. if you don`t want to, or can`t, leave them completely from mesh, you can just leave them uninitialized. I guess default value is 0x000000, but that doesn`t matter. I don`t know what do you do with colors in your shaders, but if you need the same color on every vertex, you can simply add constant to vertex shader or hard-code it.

btw, what are you working on?

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Hi again, im currently working on building a 3d engine library that now work
very well on OpenGL. It can load models, assign texture to them, and
render them with very little line of code. The class CModels handle all the
loading of the model data and the texture, as well as most of the renderaing part.
I also use my own model format, so that why i needed to keep my array separately.

For example, here is the .h and .cpp file of a simple project rendering one lit and textured model:

-MyProject.h

#pragma comment(lib, "Vortez3DEngine.lib")

#include "Vortez3DEngine.h"
#include "Common.h"
#include "SafeKill.h"

class CEngine : public CVortez3DEngine {
public:
void InitEngineExt();
void ShutdownEngineExt();
void RenderScene();
void UpdateScene(float ElapsedTime);
};









-MyProject.cpp

#include "MyProject.h"

CEngine *pEngine;
CModel MyModel;

int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
pEngine = new CEngine;

if(pEngine->InitEngine(&hInstance, 0,0,800,600,1)){
pEngine->StartEngine();
}
pEngine->ShutdownEngine();

SAFE_DELETE_OBJECT(pEngine);

return 0;
}

void CEngine::InitEngineExt()
{
pEngine->Camera.SetDefaultValue(1.0f,2500.0f, 0.0f,60.0f, 0.0f,0.0f,0.0f, 100.0f, 1.0f,250.0f, 0.0f,360.0f,-90.0f,90.0f);

MyModel.LoadModelFromFile("MyModel.M3D");
MyModel.LoadPrimaryTextureID("MyTexture.bmp", 0, 0);
}

void CEngine::ShutdownEngineExt()
{
MyModel.FreeModelData();
}


void CEngine::RenderScene()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

// Set OpenGL for 3D Drawing
pEngine->Set3DMode(1, 2500);

glEnable(GL_LIGHTING);
glEnable(GL_TEXTURE_2D);
glEnable(GL_DEPTH_TEST);

// Set the color to pure white
glColor3f(1.0f, 1.0f, 1.0f);

// Begin 3d drawing
glPushMatrix();

pEngine->Camera.SetCamera();

//Draw the model with all the availlaible vertex buffer loaded with the model(position, tex1, tex2, normals, fog)
MyModel->DrawModel();

glPopMatrix();

// Set OpenGL for 2D Drawing
pEngine->Set2DMode();

glDisable(GL_LIGHTING);
glDisable (GL_TEXTURE_2D);
glDisable (GL_DEPTH_TEST);

//Draw the FPS
DrawFPS();

// Swap the back buffer, drawing the current scene on // the screen
SwapBuffers(pEngine->GethDC());
}


void CEngine::UpdateScene(float ElapsedTime)
{
// This function is called just before RenderScene(), // so you can update some render related data before //renderain the scene
}











The engine suppost keyboard and mouse input as well, that can be accessed by using one of the virtuals functions of the engine, and a couple of usefull function too, but i try to keep it to a minimum, making it the most versatile possible, so it's not a "true" engine(cause u have to write OpenGL/DX code...), but close enought...

Check the docs here if u want to know more:
http://www.freewebs.com/vortex666/Doc.zip

[Edited by - Vortez on October 27, 2007 2:21:55 PM]

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oh, almost forget to ask, did dx take care of deleting textures, vertex and index buffers automatically or should i call some function to free them???

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DirectX is COM based, so you need to manually release (ie call ->Release) on any object you let DirectX create for you.

Try turning DirectX debug libraries, they will be slower but you'll also get a list of memory leaks (and other useful debug info).

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