hwUnlitShader/MTexture.cpp

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// MTexture.cpp

// DESCRIPTION: Texture object, that can be mipmapped. Eventually,
//              this class will likely end up in the Maya API.
//
// AUTHOR: Christian Laforte
//

#include "MTexture.h"
#include <maya/MStatus.h>
#include <maya/MGlobal.h>
#include "MNormalMapConverter.h"

MTexture::MTexture()
{
    // Initialize everything
    m_levels = NULL;
    m_numLevels = 0;
}

#define MIN(x, y) (((x) < (y)) ? (x) : (y) )
#define MAX(x, y) (((x) > (y)) ? (x) : (y) )

bool MTexture::load(MString filename, 
                    MTexture::Type type, 
                    bool mipmapped /* = true */,
                    GLenum target /* = GL_TEXTURE_2D */)
{
    MImage image;
    MStatus stat = image.readFromFile(filename);
    if (!stat)
    {
        MGlobal::displayWarning("In MTexture::load(), file not found: \"" + filename + "\".");
        return false;
    }

    return set( image, type, mipmapped, target );
}

bool MTexture::set(MImage &image, Type type, 
                   bool mipmapped /* = true */, 
                   GLenum target /* = GL_TEXTURE_2D) */)
{
    unsigned int i; // used as a temporary index.

    // Store the type of texture, and derive other parameters.
    // (Depth is assumed to be 4 bytes per pixel RGBA.
    // MImage always returns that pixel format anyway.)
    m_type = type;
    if ( (m_type == RGBA) || (m_type == NMAP) )
    {
        m_internalFormat = GL_RGBA8;
        m_format = GL_RGBA;
        m_componentFormat = GL_UNSIGNED_BYTE;
    }
    else if (m_type == HILO)
    {
#if NVIDIA_SPECIFIC
        m_internalFormat = GL_SIGNED_HILO_NV;
        m_format = GL_HILO_NV;
        m_componentFormat = GL_SHORT;
#endif
    }
    else assert(0);


    // Get the dimension of the texture.
    MStatus stat = image.getSize(m_width, m_height);
    assert(stat);
    m_mipmapped = mipmapped;

    unsigned int maxWidthLevels  = highestPowerOf2(m_width);
    unsigned int maxHeightLevels = highestPowerOf2(m_height);

    // Standard OpenGL doesn't accept width or height that are not power of 2.
    // If that's the case we resize the picture to the closest larger valid rectangle.
    bool widthIsExponent = (m_width == (unsigned int) (1 << maxWidthLevels));
    bool heightIsExponent = (m_height == (unsigned int) (1 << maxHeightLevels));

    if (!widthIsExponent || !heightIsExponent)
    {
        // Calculate the new width/height.
        if (!widthIsExponent)
            maxWidthLevels++;
        if (!heightIsExponent)
            maxHeightLevels++;

        // Resize the image, without bothering to preserve the aspect ratio.
        m_width = 1 << maxWidthLevels;
        m_height = 1 << maxHeightLevels;
        image.resize(m_width, m_height, false);
    }

    // Deallocate any existing levels
    if (m_levels != NULL)
    {
        for (i=0; i < m_numLevels; i++)
        {
            if (m_levels[i])
            {
                delete [] m_levels[i];
                m_levels[i] = NULL;
            }
        }       
        delete [] m_levels;
    }

    // The number of mipmap levels cannot be greater than the exponent of width or height.
    // The number of mipmap levels is 1 for a non-mipmapped texture.
    // For mipmapped textures, m_numLevels = max level + 1.
    m_numLevels = mipmapped ? MAX(maxWidthLevels, maxHeightLevels) + 1 : 1;

    // Allocate the proper amount of memory, for the base level and the mipmaps.
    m_levels = new unsigned char* [m_numLevels];
    for (i=0; i < m_numLevels; i++)
    {
        m_levels[i] = new unsigned char [width(i) * height(i) * 4];
    }

    // Copy the base level. (the actual file texture)
    memcpy(m_levels[0], image.pixels(), m_width * m_height * 4);
    
    // Create the mipmapped levels.
    // NOTE REGARDING THE width_ratio and height_ratio:
    //     The smallest mipmap levels of non-square textures must be handled
    // carefully. Say we have a 8x2 texture. Mipmap levels will be
    // 4x1, 2x1, 1x1. We cannot simply multiply the current st coordinate by
    // 2 like we do for square textures to find the source st coordinates, 
    // or we'll end up fetching outside of the source level. Instead, we
    // multiply the target s, t coordinates by the width and height ratio respectively.
    for (unsigned int current_level = 1; current_level < m_numLevels; current_level++)
    {
        unsigned int width_ratio = width(i-1) / width(i);
        unsigned int height_ratio = height(i-1) / height(i-1);
        unsigned int previous_level = current_level - 1;

        for (unsigned int target_t = 0; target_t < height(current_level); target_t++)
        {
            for (unsigned int target_s = 0; target_s < width(current_level); target_s++)
            {
                // The st coordinates from the source level.
                unsigned int source_s = target_s * width_ratio;
                unsigned int source_t = target_t * height_ratio;
                unsigned int source_s2 = source_s + ((width_ratio == 2) ? 1 : 0);
                unsigned int source_t2 = source_t + ((height_ratio == 2) ? 1 : 0);

                unsigned char *destination  = internalFetch(target_s,   target_t,   current_level);
                unsigned char *source1      = internalFetch(source_s,   source_t,   previous_level);
                unsigned char *source2      = internalFetch(source_s2,  source_t,   previous_level);
                unsigned char *source3      = internalFetch(source_s,   source_t2,  previous_level);
                unsigned char *source4      = internalFetch(source_s2,  source_t2,  previous_level);

                // Average byte per byte.
                unsigned int average1 = (*source1++ + *source2++ + *source3++ + *source4++) / 4;
                *destination++ = average1;

                unsigned int average2 = (*source1++ + *source2++ + *source3++ + *source4++) / 4;
                *destination++ = average2;

                unsigned int average3 = (*source1++ + *source2++ + *source3++ + *source4++) / 4;
                *destination++ = average3;

                unsigned int average4 = (*source1++ + *source2++ + *source3++ + *source4++) / 4;
                *destination++ = average4;
            }
        }
    }

    if( type == NMAP )
    {
        // Convert each level to the NORMAL map format
        //
        MNormalMapConverter mapConverter;

        for (unsigned int i = 0; i < m_numLevels; i++)
        {
            mapConverter.convertToNormalMap( m_levels[i], width(i), height(i), MNormalMapConverter::RGBA, 2.0f );
        }
    }

    specify(target);

    return true;
}

bool MTexture::specify(GLenum target /* = GL_TEXTURE_2D */)
{
    assert(glGetError() == GL_NO_ERROR);

    m_texObj.bind();

    assert(glGetError() == GL_NO_ERROR);

    for (unsigned int i=0; i < m_numLevels; i++)
    {
        glTexImage2D(target, i, m_internalFormat, width(i), height(i), 0,
                     m_format, m_componentFormat, m_levels[i]);

        assert(glGetError() == GL_NO_ERROR);
    }

    if (mipmapped())
    {
        // Mipmapping enabled
        m_texObj.parameter(GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
        assert(glGetError() == GL_NO_ERROR);

        m_texObj.parameter(GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        assert(glGetError() == GL_NO_ERROR);
    }
    else
    {
        m_texObj.parameter(GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        m_texObj.parameter(GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    }

    m_texObj.parameter(GL_TEXTURE_WRAP_S, GL_CLAMP);
    m_texObj.parameter(GL_TEXTURE_WRAP_T, GL_CLAMP);

    return true;
}

bool MTexture::bind()
{
    m_texObj.bind();
    //specify(GL_TEXTURE_2D);

    return true;
}


int highestPowerOf2(int num)
{
    int power = 0;

    while (num > 1)
    {
        power++;
        num = num >> 1;
    }

    return power;
}