Question

I been working in a project with a team for a Software Engineering class and we think that using the parallax scrolling will help our game to look really nice but we are not really sure if our idea for implementation it’s the correct one, so I hope that someon will give us some guidance about our plan.

First, we have three classes, Level, Tileset, Layer, the first one has two vectors of Layers and Tilesets, so our idea is load all the data from a TMX file of the first level in a vector>, but we only draw the part of the map that it’s currently in camera, so inside a cycle we draw every layer, but we’re not sure how defined a velocity for each layer so the parallax scrolling works like it supposed.

PD: If someone need more information, don’t doubt in ask.

Answer 1

Sorry for the late answer. I already find out the problem, I leave the new code so maybe someone will find this useful. The problem was handling the different offset in each row of the tilemap, but now it’s solved.

void Tilemap::drawTilemap(int indexTileset)
{
    GLfloat offsetXTemp = offset.x;

    offsetXTemp = transformOffsetXToIntervalValues(offset.x);

    GLfloat variableSizeTile = 32.f;

    GLfloat widthTilesetImage = tilesetList.at(indexTileset).getWidthImage();
    GLfloat heightTilesetImage = tilesetList.at(indexTileset).getHeightImage();

    int widthMap = (1280 / (int)sizeTiles) + 1;
    int heigthMap = (int) ceil( 720.0f / sizeTiles );

    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    glEnableClientState( GL_VERTEX_ARRAY );
    glEnableClientState( GL_TEXTURE_COORD_ARRAY );  

    glBindTexture( GL_TEXTURE_2D, tilesetList.at(indexTileset).getTexture() );

    GLfloat posXPrevious = 0.0f, posXPreviousOnTexture = 0.0f;

    for (int i = 0; i < heigthMap; i++)
    {
        int startX = (int)floor(offset.x/sizeTiles);
        posXPrevious = 0.0f;

        posXPrevious -= offsetXTemp;
        variableSizeTile = 32.f;

        for (int j = 0; j < widthMap; j++) 
        {
            if ( startX == widthLevelInTiles )
            {
                break;
            }

            int frameIndex = layerMap[i][startX].getID();

            if ( frameIndex == 0 )
            { 
                startX++;
                variableSizeTile = 32.f;
                posXPrevious = posXPrevious + variableSizeTile;

                continue; 
            }

            if ( j == 0 && offsetXTemp != sizeTiles)
            {
                posXPreviousOnTexture = offsetXTemp/widthTilesetImage;
                variableSizeTile -= offsetXTemp;
                posXPrevious = 0.0f;
            }

            else 
            { 
                variableSizeTile = 32.f; 
                posXPreviousOnTexture = 0.0f;
            }

            if ( j == 40 )
            {
                variableSizeTile = offsetXTemp;
            }

            frameIndex -= 1;

            const GLfloat tileX = posXPrevious;
            const GLfloat tileY = sizeTiles * i;
            posXPrevious = tileX + variableSizeTile;

            const GLfloat verts[] = {
                    tileX, tileY,
                    tileX + variableSizeTile, tileY,
                    tileX + variableSizeTile, tileY + sizeTiles,
                    tileX, tileY + sizeTiles
            };

            const GLfloat textureWidth = variableSizeTile / (GLfloat)widthTilesetImage;
            const GLfloat textureHeight = sizeTiles / (GLfloat)heightTilesetImage;
            const int numFramePerRow = (int)widthTilesetImage / (int)sizeTiles;
            const GLfloat textureX = ( (frameIndex % numFramePerRow) * sizeTiles/(GLfloat)widthTilesetImage ) 
                                    + posXPreviousOnTexture;
            const GLfloat textureY = ( frameIndex / numFramePerRow ) * textureHeight;

            const GLfloat texVerts[] = {
                    textureX, textureY,
                    textureX + textureWidth, textureY,
                    textureX + textureWidth, textureY + textureHeight,
                    textureX, textureY + textureHeight
            };

            glVertexPointer(2, GL_FLOAT, 0, verts);
            glTexCoordPointer(2, GL_FLOAT, 0, texVerts);
            glDrawArrays(GL_QUADS, 0, 4);

            startX++;
        }   
    }

    glDisableClientState( GL_VERTEX_ARRAY );            
    glDisableClientState( GL_TEXTURE_COORD_ARRAY );
}