Drawing a Grid(Terrainlike)

m4gnus · 2005-05-29T04:54:34

Hi Finally the Inputsystem for my engine works so now i just want to render a simple grid with an indexed Trianglelist...I tried to keep everything as clear as possible so i first wrote a basemsh class which just contains an Index-,a Vertexbuffer and a DWORD for the FVF...every class that will be renders should be a child of this class so i thought i'll make a very basic terrain class which just creates a grid of variable size with a variable number of subdivions... but something is worng with it..it definitly has something to do with the creation of the Vertex and Indexbuffer because if i fill 'em manually it works fine... My terrain Class: #include "stdafx.h" #include ".\terrain.h" #include "ngEngine.h" Terrain::Terrain(void) { FVF=D3DFVF_XYZ|D3DFVF_DIFFUSE; } Terrain::~Terrain(void) { } void Terrain::Create(ngEngine *engine,D3DXVECTOR3 StartPoint,float xSize,float zSize,int xRes,int zRes) { m_pEngine=engine; float RowHeight=zSize/zRes; float ColWidth=xSize/xRes; CreateVertices(StartPoint,RowHeight,ColWidth,xRes,zRes); CreateIndices(xRes,zRes); ConstructBuffers(); } void Terrain::CreateVertices(D3DXVECTOR3 StartPoint,float RowHeight,float ColWidth,int xCount,int zCount) { for(int j=0;j<=zCount;j++) //<--for every Row do: { for(int i=0;i<=xCount;i++) //<--for every Vert do: { TerrainVert Vertex; Vertex.x=StartPoint.x+i*ColWidth; Vertex.y=StartPoint.y; //<---Terrain Height Vertex.z=StartPoint.z+j*RowHeight; Vertex.color=0xff00ff00; Verts.push_back(Vertex); } } } void Terrain::CreateIndices(int xRes, int yRes) { for(int j=0;j<=yRes-1;j++) //<--For Every Row do: { for(int i=0;i<=xRes-1;i++) //<--For Every QUAD(!) do: { int Row=j*xRes; //First Triangle Indices.push_back(xRes*j+i+Row); Indices.push_back(i+Row); Indices.push_back(i+Row+1); //Indices.push_back(xRes*j+i+1+Row); //Second Triangle Indices.push_back(i+Row); Indices.push_back(i+1+Row); Indices.push_back(xRes*j+i+1+Row); } } } void Terrain::ConstructBuffers() { //Create VertexBuffer: if( FAILED( m_pEngine->g_pD3DDevice->CreateVertexBuffer(Verts.size()*sizeof(std::vector<TerrainVert>::value_type), 0, FVF, D3DPOOL_DEFAULT, &pVBuffer, //<---inherited from BaseMesh NULL ) ) ) { MessageBox(0,"Fetter Error1!","Error",0); PostQuitMessage(1); } VOID *pVData; pVBuffer->Lock(0,sizeof(std::vector<TerrainVert>::value_type),(void**)&pVData,0); //lock buffer std::vector<TerrainVert>::pointer Vptr = &Verts[0]; memcpy(pVData,Vptr,Verts.size()*sizeof(std::vector<TerrainVert>::value_type)); //copy data to buffer pVBuffer->Unlock(); //Create IndexBuffer: if(FAILED(m_pEngine->g_pD3DDevice->CreateIndexBuffer(Indices.size()*sizeof(std::vector<short>::value_type),D3DUSAGE_WRITEONLY,D3DFMT_INDEX16,D3DPOOL_MANAGED,&pIBuffer,NULL))) { MessageBox(0,"Fetter Error2!","Error",0); PostQuitMessage(1); } VOID *pIData; pIBuffer->Lock(0,sizeof(std::vector<short>::value_type),(void**)&pIData,0); //lock buffer std::vector<short>::pointer Iptr = &Indices[0]; memcpy(pIData,Iptr,Indices.size()*sizeof(std::vector<short>::value_type)); //copy data to buffer pIBuffer->Unlock(); } void Terrain::render() { m_pEngine->g_pD3DDevice->SetFVF(FVF); //<---inherited from BaseMesh m_pEngine->g_pD3DDevice->SetStreamSource(0,pVBuffer,0,sizeof(std::vector<TerrainVert>::value_type)); m_pEngine->g_pD3DDevice->SetIndices(pIBuffer); m_pEngine->g_pD3DDevice->DrawIndexedPrimitive(D3DPT_TRIANGLELIST,0,0,Verts.size(),0,(xDivs-1)*(zDivs-1)*2); } regards, m4gnus

Graphics and GPU Programming Programming

Started by m4gnus May 25, 2005 01:55 PM

17 comments, last by m4gnus 18 years, 11 months ago

m4gnus

240

Author

May 26, 2005 12:27 PM

ok the error has to be in the vertex creation because if i create them by hand for a grid with xRes=2 and zRes=2 (a simple quad) and let the CreateIndices function create the indices everything works fine!

regards,
m4gnus

"There are 10 types of people in the world... those who understand binary and those who don't."

Kippesoep

892

May 26, 2005 03:54 PM

By "set up" I mean "given a value".

That's the thing about the debugger: you can inspect the value of anything in memory. You'd be able to see what the coordinates are of the vectors being generated. What you have is a runtime error. Non-fatal, but a runtime error nonetheless.

Another thing you may want to check out: you're only locking one vertex in ConstructBuffers:

pVBuffer->Lock(0,sizeof(std::vector<TerrainVert>::value_type),&pVData,0);

You probably want to lock the entire buffer:

pVBuffer->Lock(0,0,&pVData,0);

Kippesoep

m4gnus

240

Author

May 28, 2005 11:28 AM

oops..thx i fixed that but my prob is still there and i don't really know why this:

	for(int j=0;j<=zCount;j++)   //<--for every Row do:	{		for(int i=0;i<=xCount;i++) //<--for every Vert do:		{			TerrainVert Vertex;			Vertex.x=StartPoint.x+i*ColWidth;			Vertex.y=StartPoint.y;            //<---Terrain Height			Vertex.z=StartPoint.z+j*RowHeight;			Vertex.color=0xff00ff00;			Verts.push_back(Vertex);		}	}

does something different than:

TerrainVert vertex;vertex.x=0.0f;vertex.y=-10.0f;vertex.z=100.0f;vertex.color=0xff00ff00;TerrainVert vertex2;vertex2.x=400.0f;vertex2.y=-10.0f;vertex2.z=100.0f;vertex2.color=0xff00ff00;TerrainVert vertex3;vertex3.x=0.0f;vertex3.y=-10.0f;vertex3.z=-300.0f;vertex3.color=0xff0000ff;TerrainVert vertex4;vertex4.x=400.0f;vertex4.y=-10.0f;vertex4.z=-300.0f;vertex4.color=0xffff0000;Verts.push_back(vertex);Verts.push_back(vertex2);Verts.push_back(vertex3);Verts.push_back(vertex4);

if StartPoint is set to 0,-10,100, xSize and zSize to 400 and xRes+zRes to 2...if i do it by hand it create a large wuad like i want but the double loop just create 1 strange triangle. Can somebody tell me what's the difference betweem these too?

regards,
m4gnus

"There are 10 types of people in the world... those who understand binary and those who don't."

Kippesoep

892

May 28, 2005 12:39 PM

It does something different because that's what you're telling it to do. To get those 4 vertices, you'd have to set xSize to 400, zSize to -400 (negative!!), xRes and zRes to 1.

It's probably the negative zSize that is causing the problem. If you want z to go along the negative axis, but specify a positive zSive, all your triangles are reversed and will be backface-culled.

Kippesoep

m4gnus

240

Author

May 28, 2005 01:23 PM

no backface culling is turned off...and are you sure that i have to set xRes+zRes to 1? these 2 values are not the number of quad-columns(/rows) but the number of vertex-columns(/rows)

btw it would it help if i post a screenshot like it should be(with manual filled vertexbuffer) and a screenshot with that strange triangle when generating the vertices.

if i change zRes to -zRes it draws nothing...

regards,
m4gnus

"There are 10 types of people in the world... those who understand binary and those who don't."

Kippesoep

892

May 28, 2005 02:17 PM

The numbers I gave you are the way to generate the four vertices you created manually. Step through it with the debugger and you'll see.

BTW, instead of xDivs and zDivs, I meant to use those values for xRes and zRes (why do you have two different variables refering to the same concept with slightly different semantics without any good link in the class that uses them?).

Kippesoep

m4gnus

240

Author

May 28, 2005 03:10 PM

i mean that for a quad you have to use xRes,zRes=2 because these values are the vertices per row/column not the quads per row/column and because a simple quad consists of 4 vertices(2 in 1 row, 2 rows) i need to set xRes,zRes to 2. if i would set 'em to 1 i would have a point...i know that you would ussually expect it to be the number of quads per row, so i'll change it as soon as everything works so far...

btw i changed xDivs,zDivs to xRes,zRes now...

"There are 10 types of people in the world... those who understand binary and those who don't."

Kippesoep

892

May 28, 2005 05:40 PM

In the code you gave, to get one quad, you need to set xDivs and zDivs to 2, and xRes and yRes to 1. (Always: xDivs = xRes + 1; zDivs = zRes + 1;). Again, in the code shown, there is nothing that shows where xDivs and zDivs come from. It is not set anywhere, so it's likely to be a global variable. Bad idea to use global variables like that inside your class. Basically: get rid of that. What I'd expect to see (and recommend you do) is something like:

void Terrain::Create (ngEngine *engine, D3DXVECTOR3 StartPoint, float xSize, float zSize, int xRes, int zRes){    //Store values    m_pEngine = engine;    m_xRes = xRes;    m_zRes = zRes;        //Create vertices    CreateVertices (StartPoint, xSize/m_xRes, zSize/m_zRes);    //Create indices    CreateIndices ();}void Terrain::CreateVertices (D3DXVECTOR3 StartPoint, float RowHeight, float ColWidth){    for (int j = 0; j <= m_zRes; ++j)    {        for (int i = 0; i <= m_xRes; ++i)        {            TerrainVert Vertex;            Vertex.x = StartPoint.x + i * ColWidth;            Vertex.y = StartPoint.y;            Vertex.z = StartPoint.z + j * RowHeight;            Vertex.color = 0xDD00DD00;            Verts.push_back (Vertex);        }    }}void Terrain::CreateIndices (){    for (int j = 0; j < m_zRes; ++j)    {        for (int i = 0; i < m_xRes; ++i)        {            /* ... */        }    }}void Terrain::render() {    m_pEngine->g_pD3DDevice->DrawIndexedPrimitive (D3DPT_TRIANGLELIST, 0, 0, Verts.size (), 0, m_zRes * m_xRes * 2);}

This places the terrain resolution in the class, where it belongs, and doesn't cause the confusion.

If the numbers I gave you don't work, then something is wrong elsewhere. They will generate the exact same vertices you listed manually. Let me spell out the program flow for you:

terrain->Create (g_Engine, D3DXVECTOR3 (0, -10, 100), 400, -400, 1, 1);//In terrain::Createfloat RowHeight=-400/*zSize/zRes*/;float ColWidth=400/*xSize/xRes*/;CreateVertices(D3DXVECTOR3 (0, -10, 100), -400, 400, 1, 1);//In CreateVertices/* j = 0, zCount == 1 *//* i = 0; xCount == 1 */Vertex.x = 0; //(StartPoint.x+i*ColWidth) = 0 + 0 * 400 = 0Vertex.y = -10;Vertex.z = 100; //(StartPoint.z+j*RowHeight) = 100 + 0 * -400 = 100/* j = 0, zCount == 1 *//* i = 1; xCount == 1 */Vertex.x = 400; //(StartPoint.x+i*ColWidth) = 0 + 1 * 400 = 400Vertex.y = -10;Vertex.z = 100; //(StartPoint.z+j*RowHeight) = 100 + 0 * -400 = 100/* j = 1, zCount == 1 *//* i = 0; xCount == 1 */Vertex.x = 0; //(StartPoint.x+i*ColWidth) = 0 + 0 * 400 = 0Vertex.y = -10;Vertex.z = -300; //(StartPoint.z+j*RowHeight) = 100 + 1 * -400 = -300/* j = 1, zCount == 1 *//* i = 1; xCount == 1 */Vertex.x = 400; //(StartPoint.x+i*ColWidth) = 0 + 1 * 400 = 400Vertex.y = -10;Vertex.z = -300; //(StartPoint.z+j*RowHeight) = 100 + 1 * -400 = -300

So, you get (0,-10,100) (400,-10,100) (0,-10,300) (400,-10,-300), which is exactly what you wanted.

Kippesoep

m4gnus

240

Author

May 29, 2005 04:54 AM

everything works fine now...the xRes and zRes variables now really are the fertex rows+columns...just had to use for(int i=0;i<xCount;i++) instead of for(int i=0;i<=xCount;i++)

thank you

Edit: oops it only works for xRes,zRes=2 but if i set it to higher values one quad is missing..

regards,
m4gnus

"There are 10 types of people in the world... those who understand binary and those who don't."

Drawing a Grid(Terrainlike)

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